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Cover Page - USD ($)	12 Months Ended
Cover Page - USD ($)	Dec. 31, 2019	Mar. 26, 2020	Jun. 30, 2019
Cover [Abstract]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2019
Document Transition Report	false
Entity File Number	1-31398
Entity Registrant Name	NATURAL GAS SERVICES GROUP, INC.
Entity Incorporation, State or Country Code	CO
Entity Tax Identification Number	75-2811855
Entity Address, Address Line One	404 Veterans Airpark Lane, Suite 300
Entity Address, City or Town	Midland
Entity Address, State or Province	TX
Entity Address, Postal Zip Code	79705
City Area Code	(432)
Local Phone Number	262-2700
Title of 12(b) Security	Common Stock, $.01 par value
Trading Symbol	NGS
Security Exchange Name	NYSE
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Public Float			$ 216,747,630
Entity Common Stock, Shares Outstanding		13,382,569
Documents Incorporated by Reference	Certain information called for in Items 10, 11, 12, 13 and 14 of Part III are incorporated by reference to the registrant’s definitive proxy statement for the annual meeting of shareholders expected to be held on June 25, 2020.
Amendment Flag	false
Entity Central Index Key	0001084991
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	FY

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Current Assets:
Cash and cash equivalents	$ 11,592	$ 52,628
Trade accounts receivable, net of allowance for doubtful accounts of $918 and $291, respectively	9,106	7,219
Inventory	21,080	30,190
Prepaid income taxes	40	3,188
Prepaid expenses and other	597	1,696
Total current assets	42,415	94,921
Long-Term Inventory, net of allowance for obsolescence of $24 and $19, respectively	1,068	3,980
Rental equipment, net of accumulated depreciation of $162,348 and $165,459, respectively	217,742	176,106
Property and equipment, net of accumulated depreciation of $12,847 and $11,570, respectively	21,869	16,644
Right of use assets - operating leases, net of accumulated amortization $158	604	0
Goodwill	0	10,039
Intangibles, net of accumulated amortization of $1,883 and $1,758, respectively	1,276	1,401
Other assets	1,603	1,109
Total assets	286,577	304,200
Current Liabilities:
Accounts payable	1,975	2,122
Accrued liabilities	2,287	8,743
Line of credit	417	0
Current operating leases	189	0
Deferred income	640	81
Total current liabilities	5,508	10,946
Line of credit	0	417
Deferred income tax liability	31,243	31,906
Long-term operating leases	415	0
Other long-term liabilities	1,718	1,699
Total liabilities	38,884	44,968
Commitments and contingencies (Notes 5, 16 and 19)
Stockholders’ Equity:
Preferred stock, 5,000 shares authorized, no shares issued or outstanding	0	0
Common stock, 30,000 shares authorized, par value $0.01; 13,178 and 13,005 shares issued, respectively	132	130
Additional paid-in capital	110,573	107,760
Retained earnings	137,478	151,342
Treasury shares, at cost, 38 shares	(490)	0
Total stockholders' equity	247,693	259,232
Total liabilities and stockholders' equity	$ 286,577	$ 304,200

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Current Assets:
Allowance for doubtful accounts	$ 918	$ 291
Allowance for inventory obsolescence	24	19
Assets, Noncurrent [Abstract]
Accumulated depreciation, rental equipment	162,348	165,459
Accumulated depreciation, property and equipment	12,847	11,570
Accumulated amortization, operating lease right of use assets	158
Accumulated amortization, intangibles	$ 1,883	$ 1,758
Stockholders’ Equity:
Preferred stock, shares authorized (in shares)	5,000,000	5,000,000
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	30,000,000	30,000,000
Common stock, shares issued (in shares)	13,178,000	13,005,000
Common stock, shares outstanding (in shares)	13,178,000	13,005,000
Treasury shares (in shares)	38,000

Consolidated Statements of Operations - USD ($) shares in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenue:
Revenues	$ 78,444,000	$ 65,478,000	$ 67,693,000
Operating costs and expenses:
Cost of rentals, exclusive of depreciation stated separately below	27,583,000	21,860,000	18,160,000
Cost of sales, exclusive of depreciation stated separately below	16,097,000	12,564,000	16,022,000
Cost of service and maintenance, exclusive of depreciation stated separately below	630,000	385,000	370,000
Selling, general and administrative expenses	10,710,000	9,096,000	10,081,000
Depreciation and amortization	23,268,000	22,080,000	21,316,000
Impairments	10,039,000	0	0
Inventory allowance	3,758,000	0	273,000
Retirement of rental equipment	1,512,000	0	0
Total operating costs and expenses	93,597,000	65,985,000	66,222,000
Operating (loss) income	(15,153,000)	(507,000)	1,471,000
Other income (expense):
Interest expense	(15,000)	(69,000)	(14,000)
Other income	611,000	182,000	50,000
Total other income, net	596,000	113,000	36,000
(Loss) income before income taxes:	(14,557,000)	(394,000)	1,507,000
(Provision for) benefit from income taxes:
Current	31,000	242,000	(3,288,000)
Deferred	662,000	(314,000)	21,575,000
Total income tax benefit (expense)	693,000	(72,000)	18,287,000
Net (loss) income	$ (13,864,000)	$ (466,000)	$ 19,794,000
(Loss) earnings per share:
Earnings (loss) per share - Basic (in dollars per share)	$ (1.06)	$ (0.04)	$ 1.54
Earnings (loss) per share - Diluted (in dollars per share)	$ (1.06)	$ (0.04)	$ 1.51
Weighted average shares outstanding:
Weighted average shares outstanding, Basic (in shares)	13,114	12,965	12,831
Weighted average shares outstanding, Diluted (in shares)	13,114	12,965	13,110
Rental income
Revenue:
Revenues	$ 56,701,000	$ 47,766,000	$ 46,046,000
Sales
Revenue:
Revenues	19,763,000	16,269,000	20,208,000
Service and maintenance income
Revenue:
Revenues	$ 1,980,000	$ 1,443,000	$ 1,439,000

Consolidated Statements of Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Preferred Stock	Common Stock	Additional Paid-In Capital	Retained Earnings	Treasury Stock
Balance, beginning of period (in shares) at Dec. 31, 2016		0	12,764			0
Balance, beginning of period at Dec. 31, 2016	$ 232,954	$ 0	$ 128	$ 100,812	$ 132,014	$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of common stock options, shares (in shares)			56
Exercise of common stock options	1,120			1,120
Compensation expense on common stock options	363			363
Issuance of restricted stock, shares (in shares)			60
Issuance of restricted stock	0
Compensation expense on restricted common stock	3,675		$ 1	3,674
Taxes paid related to net shares settlement of equity awards	(644)			(644)
Net (loss) income	19,794				19,794
Balance, end of period (in shares) at Dec. 31, 2017		0	12,880			0
Balance, end of period at Dec. 31, 2017	257,262	$ 0	$ 129	105,325	151,808	$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of common stock options, shares (in shares)			38
Exercise of common stock options	680			680
Compensation expense on common stock options	159			159
Issuance of restricted stock, shares (in shares)			87
Issuance of restricted stock	0
Compensation expense on restricted common stock	2,226		$ 1	2,225
Taxes paid related to net shares settlement of equity awards	(629)			(629)
Net (loss) income	(466)				(466)
Balance, end of period (in shares) at Dec. 31, 2018		0	13,005			0
Balance, end of period at Dec. 31, 2018	259,232	$ 0	$ 130	107,760	151,342	$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of common stock options, shares (in shares)			56
Exercise of common stock options	506		$ 1	505
Compensation expense on common stock options	124			124
Issuance of restricted stock, shares (in shares)			117
Issuance of restricted stock	0
Compensation expense on restricted common stock	2,458		$ 1	2,457
Taxes paid related to net shares settlement of equity awards	(273)			(273)
Purchase of treasury shares (in shares)						38
Purchase of treasury shares	(490)					$ (490)
Net (loss) income	(13,864)				(13,864)
Balance, end of period (in shares) at Dec. 31, 2019		0	13,178			38
Balance, end of period at Dec. 31, 2019	$ 247,693	$ 0	$ 132	$ 110,573	$ 137,478	$ (490)

Consolidated Statements of Cash Flows - USD ($)	12 Months Ended
Consolidated Statements of Cash Flows - USD ($)	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
CASH FLOWS FROM OPERATING ACTIVITIES:
Net (loss) income	$ (13,864,000)	$ (466,000)	$ 19,794,000
Adjustments to reconcile net (loss) income to net cash provided by operating activities:
Depreciation and amortization	23,268,000	22,080,000	21,316,000
Deferred taxes	(662,000)	314,000	(21,575,000)
Gain on disposal of assets	(55,000)	(69,000)	(87,000)
Retirement of rental equipment	1,512,000	0	0
Bad debt allowance (recovery)	664,000	(185,000)	90,000
Inventory allowance	3,758,000	0	273,000
Impairments	10,039,000	0	0
Stock-based compensation	2,582,000	2,385,000	4,038,000
(Gain) loss on company owned life insurance	(218,800)	153,900	(67,000)
Changes in operating assets and liabilities:
Trade accounts receivables	(2,550,000)	1,500,000	(1,246,000)
Inventory	8,256,000	(5,102,000)	(5,221,000)
Prepaid income taxes and prepaid expenses	3,288,000	(578,000)	(1,852,000)
Changes in operating assets and liabilities:
Accounts payable and accrued liabilities	(7,225,000)	3,597,000	3,410,000
Deferred income	559,000	(104,000)	(2,040,000)
Other	61,000	163,000	666,000
NET CASH PROVIDED BY OPERATING ACTIVITIES	29,412,000	23,689,000	17,499,000
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchase of rental equipment, property and other equipment	(69,938,000)	(40,065,000)	(13,536,000)
Purchase of company owned life insurance	(302,000)	(289,000)	(620,000)
Proceeds from insurance claim	35,000	0	1,231,000
Proceeds from sale of property and equipment	30,000	69,000	87,000
NET CASH USED IN INVESTING ACTIVITIES	(70,175,000)	(40,285,000)	(12,838,000)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds of other long-term liabilities	(16,000)	(35,000)	(23,000)
Proceeds from exercise of stock options	506,000	680,000	1,120,000
Purchase of treasury shares	(490,000)	0	0
Taxes paid related to net share settlement of equity awards	(273,000)	(629,000)	(644,000)
NET CASH (USED IN) PROVIDED BY FINANCING ACTIVITIES	(273,000)	16,000	453,000
NET CHANGE IN CASH AND CASH EQUIVALENTS	(41,036,000)	(16,580,000)	5,114,000
CASH AND CASH EQUIVALENTS AT BEGINNING OF PERIOD	52,628,000	69,208,000	64,094,000
CASH AND CASH EQUIVALENTS AT END OF PERIOD	11,592,000	52,628,000	69,208,000
SUPPLEMENTAL DISCLOSURE OF CASH FLOW INFORMATION:
Interest paid	39,000	14,000	14,000
Income taxes paid	275,000	85,000	3,725,000
NON-CASH TRANSACTIONS
Transfer of rental equipment to inventory	836,000	144,000	55,000
Transfer of inventory to rental equipment	1,184,000	0	0
Transfer of prepaids to rental equipment and inventory	958,000	$ 0	$ 0
Right of use asset acquired through an operating lease	$ 762,000

Organization, Consolidation and Presentation of Financial Statements	12 Months Ended
	Dec. 31, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Description of Business	Description of BusinessNatural Gas Services Group, Inc. (the "Company", “NGS”, "Natural Gas Services Group", "we" or "our") (a Colorado corporation), is a leading provider of natural gas compression equipment and services to the energy industry. The Company manufactures, fabricates, rents, sells and maintains natural gas compressors and flare systems for oil and natural gas production and plant facilities. NGS is headquartered in Midland, Texas, with fabrication facilities located in Tulsa, Oklahoma and Midland, Texas, and service facilities located in major oil and natural gas producing basins in the U.S. The Company was formed on December 17, 1998.

Summary of Significant Accounting Policies

12 Months Ended

Dec. 31, 2019

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

Principles of Consolidation

The accompanying consolidated financial statements include the accounts of the Company, its subsidiary, NGSG Properties, LLC and the rabbi trust associated with the Company’s deferred compensation plan, see Note 10. All significant intercompany accounts and transactions for the periods presented have been eliminated in consolidation.

Reclassifications

Certain prior year amounts have been reclassified to conform to the current year's presentation.

Use of Estimates

The preparation of our consolidated financial statements in conformity with generally accepted accounting principles in the United States of America requires our management to make estimates and assumptions that affect the amounts reported in these consolidated financial statements and accompanying notes. Actual results could differ from those estimates. Significant estimates include fixed asset lives, bad debt allowance and the allowance for inventory obsolescence. Additionally, NGS conducts a yearly review of impairment of long-lived assets. Throughout the review, determining factors are based on estimates that can significantly impact the carrying value of these assets. It is at least reasonably possible these estimates could be revised in the near term and the revisions could be material.

Cash Equivalents, Financial Instruments and Concentration of Credit Risks

For purposes of reporting cash flows, we consider all short-term investments with an original maturity of three months or less to be cash equivalents. We invest our cash primarily in deposits and money market funds with commercial banks. At times, cash balances at banks and financial institutions may exceed federally insured amounts. We believe that the risk to our cash balance is minimal because we have chosen a large bank with strong long-term ratings of Aa2/A+.

Accounts Receivable

Our trade receivables consist of customer obligations for the sale of compressors and flare systems due under normal trade terms, and operating leases for the use of our natural gas compressors. The receivables are not collateralized except as provided for under lease agreements. However, we typically require deposits of as much as 50% or use of progress payments for large custom sales contracts. We perform ongoing credit evaluations of our customers and adjust credit limits based on management's assessment of the customer's financial condition and payment history, as well as industry conditions and general economic conditions. We continuously monitor collections and payments from our customers, and maintain a provision for estimated credit losses based upon our historical experience and any specific customer collection issues that we have identified. While such credit losses have historically been within our expectations and the provisions established, we cannot guarantee that we will continue to experience the same credit loss rates that we have in the past. One customer accounted for 35% and 26% of our accounts receivable as of December 31, 2019 and 2018, respectively. A significant change in the liquidity or financial position of this customer could have a material adverse impact on the collectability of our accounts receivable and our future operating results. The allowance for doubtful accounts was $918,000 and $291,000 at December 31, 2019 and 2018, respectively. Management believes that the allowance is adequate; however, actual write-offs may exceed the recorded allowance.

A summary of our allowance for doubtful accounts is as follows:


	Year Ended December 31,
($ in thousands)	2019		2018		2017
Beginning balance	$	(291)	$	(569)	$	(597)
Accruals	(664)		—		(90)
Recoveries	—		185		—
Write-offs	37		93		118
Ending balance	(918)		(291)		(569)

Revenue Recognition Policy

The Company adopted ASC 606, Revenue from Contracts with Customers ("ASC 606") on January, 1, 2018. As a result, the Company has changed its accounting policy for revenue recognition as detailed below.

The Company applied ASC 606 using the cumulative effect method. We had no significant changes in our recognition of revenue at adoption and our review of all open revenue from contracts with customers on January 1, 2018 indicated we had no adjustment to be made. Accordingly, our consolidated financial statements for 2017 reported under ASC 605 are comparable to the consolidated financial statements for 2018 reported under ASC 606, since an adjustment was not needed, except for the respective additional disclosures as detailed below.

Revenue is measured based on a consideration specified in a customer’s contract, excluding any sale incentives and taxes collected on behalf of third parties (i.e. sales and property taxes). Revenue is recognized when a customer obtains control of promised goods or services in an amount that reflects the consideration that we expect to receive for those goods or services. To recognize revenue, we (i) identify the contract(s) with a customer; (ii) identify the performance obligations in the contract; (iii) determine the transaction price; (iv) allocate the transaction price to the performance obligations in the contract; and (v) recognize revenue when, or as, we satisfy the performance obligation(s). Shipping and handling costs incurred are accounted for as fulfillment costs and are included in cost of revenues in our Consolidated Statements of Operations.

Nature of Goods and Services

The following is a description of principal activities from which the Company generates its revenue:

Rental Revenue. The Company generates revenue from renting compressors and flare systems to our customers. These contracts, which all qualify as operating leases under ASC Topic 842, Leases (ASC 842), may also include a fee for servicing the compressor or flare during the rental contract. Our rental contracts typically range from six to 24 months, with our larger horsepower compressors having contract terms of up to 60 months. Our revenue is recognized over time, with equal monthly payments over the term of the contract. After the terms of the contract have expired, a customer may renew their contract or continue renting on a monthly basis thereafter. In accordance ASC 842 – Leases, we have applied the practical expedient ASC 842-10-15-42A, which allows the Company to combine lease and non-lease components.

Sales Revenue. The Company generates revenue by the sale of custom/fabricated compressors, flare systems and parts, as well as, exchange/rebuilding customer owned compressors and sale of used rental equipment.

Custom/fabricated compressors and flare systems - The Company designs and fabricates compressors and flares based on the customer’s specifications outlined in their contract. Though the equipment being built is customized by the customer, control under these contracts does not pass to the customer until the compressor or flare package is completed and shipped, or in accordance with a bill and hold arrangements the customer accepts title and assumes the risk and rewards of ownership. We request some of our customers to make progressive payments as the product is being built; these payments are recorded as a contract liability on the Deferred Income line on the consolidated balance sheet until control has been transferred. These contracts also may include an assurance warranty clause to guarantee the product is free from defects in material and workmanship for a set duration of time; this is a standard industry practice and is not considered a performance obligation.

From time to time, upon the customer’s written request, we recognize revenue when manufacturing is complete and the equipment is ready for shipment. At the customer’s request, we will bill the customer upon completing all performance obligations, but before shipment. The customer will formally request we ship the equipment per their direction from our manufacturing facility at a later specified date and that we segregate the equipment from our finished goods, such that they are not available to fill other orders. Per the customer’s agreement change of control is passed to the customer once the equipment

is complete and ready for shipment. We have operated using bill and hold agreements with certain customers for many years, with consistent satisfactory results for both the customer and us. The credit terms on these agreements are consistent with the credit terms on all other sales. All control is shouldered by the customer and there are no exceptions to the customer’s commitment to accept and pay for the manufactured equipment. Revenues recognized related to bill and hold arrangements for the years ended December 31, 2019 and 2018 was approximately $11.6 million and $8.3 million, respectively.

Parts - Revenue is recognized after the customer obtains control of the parts. Control is passed either by the customer taking physical possession or the parts being shipped. The amount of revenue recognized is not adjusted for expected returns, as our historical part returns have been de minimis.

Exchange or rebuilding customer owned compressors - Based on the contract, the Company will either exchange a new/rebuilt compressor for the customer’s malfunctioning compressor or rebuild the customer’s compressor. Revenue is recognized after control of the replacement compressor has transferred to the customer based on the terms of the contract, i.e., by physical delivery, delivery and installment, or shipment of the compressor.

Used compressors or flares - From time to time, a customer may request to purchase a used compressor or flare out of our rental fleet. Revenue from the sale of rental equipment is recognized when the control has passed to the customer based on the terms of the contract, i.e. when the customer has taken physical possession or the equipment has been shipped.

Service and Maintenance Revenue. The Company provides routine or call-out services on customer owned equipment. Revenue is recognized after services in the contract are rendered.

Payment terms for sales revenue and service and maintenance revenue discussed above are generally 30 to 60 days although terms for specific customers can vary. Also, the transaction prices are not subject to variable consideration constraints.

Disaggregation of Revenue

The following table shows the Company's revenue disaggregated by product or service type for the years ended:



	Year Ended December 31,
	(in thousands)
	2019		2018		2017
Compressors - sales	$	15,185	$	10,994	$	13,382
Flares - sales	959		2,535		2,755
Other (Parts/Rebuilds) - sales	3,619		2,740		4,071
Service and maintenance	1,980		1,443		1,439
Total revenue from contracts with customers	21,743		17,712		21,647
Add: ASC 842 rental revenue	56,701		47,766		46,046
Total revenue	$	78,444	$	65,478	$	67,693

Contract Balances

As of December 31, 2019 and December 31, 2018, we had the following receivables and deferred income from contracts with customers:


	December 31, 2019		December 31, 2018
	(in thousands)
Accounts Receivable
Accounts receivable - contracts with customers	$	3,061	$	2,390
Accounts receivable - ASC 842	6,963		5,120
Total Accounts Receivable	10,024		7,510
Less: Allowance for doubtful accounts	(918)		(291)
Total Accounts Receivable, net	9,106		7,219

Deferred income	$	640	$	81

The Company recognized $48,000 in revenue for the year ended December 31, 2019 that was included in deferred income at the beginning of 2019. For the period ended December 31, 2018, the Company recognized revenue of $176,000 from amounts related to sales that were included in deferred income at the beginning of 2018.

The increases (decreases) of accounts receivable and deferred income were primarily due to normal timing differences between our performance and the customers’ payments.

Transaction Price Allocated to the Remaining Performance Obligations

As of December 31, 2019, the Company did not have revenue related to unsatisfied performance obligations.

Contract Costs

The Company recognizes the incremental costs of obtaining contracts as an expense when incurred if the amortization period of the assets that the Company otherwise would have recognized is one year or less. These costs are included in selling, general and administrative expense on our Consolidated Statements of Operations.

Leases

On January 1, 2019, we adopted ASC 842 using the modified retrospective method. We recognized the cumulative effect of initially applying the new lease standard and had no adjustments to retained earnings. The comparative information has not been restated and continues to be reported under the lease accounting standard in effect for those periods.

The new lease standard requires all leases to be reported on the balance sheet as right-of-use assets and lease obligations. We elected the practical expedients permitted under the transition guidance of the new standard that retained the lease classification and initial direct costs for any leases that existed prior to adoption of the standard. We did not reassess whether any contracts or land easements entered into prior to adoption are leases or contain leases.

The cumulative effect of the changes made to our consolidated balance sheet at January 1, 2019, for the adoption of ASC 842 was as follows (in thousands):


	Balance at December 31, 2018		Adjustments due to ASC 842		Balance at January 1, 2019
Balance Sheet
Assets
Right of use assets	$	—	$	451	$	451
Liabilities
Current portion of operating leases	$	—	$	126	$	126
Long term portion of operating leases	—		325		325
Total lease liabilities	$	—	$	451	$	451

The Company, as a lessee, applies the practical expedient to not separate non-lease components from lease components, therefore, accounting for each separate lease component and its associated non-lease component, as a single lease component.

Each lease that 1) contains the same timing and pattern of transfer for lease and non-lease components; and 2) if the lease component, if accounted for separately, would be classified as an operating lease, the Company elects to not separate non-lease components from lease components.

Major Customers and Concentration of Credit Risk

Sales and rental income from Occidental Permian, LTD. ("Oxy") in 2019 and 2018 amounted to 36% and 28% of revenue, respectively. Sales and rental income to Oxy and Devon Energy Production, Inc. in 2017 amounted to 20% and 15% of revenue, respectively. No other single customer accounted for more than 10% of our revenues in 2019, 2018 or 2017. Oxy's accounts receivable balances amounted to 35% and 26% of our accounts receivable as of December 31, 2019 and 2018, respectively. No other customers amounted to more than 10% of our accounts receivable as of December 31, 2019 and 2018.

Inventory

Inventory (current and long-term) is valued at the lower of cost and net realizable value. The cost of inventories is determined by the weighted average method. We regularly review inventory quantities on hand and record a provision for excess and obsolete inventory based primarily on current and anticipated customer demand and production requirements. The Company accesses anticipated customer demand based on current and upcoming capital expenditure budgets of its major customers as well as other significant companies in the industry, along with oil and natural gas price forecasts and other factors affecting the industry. In addition, our long-term inventory consists of raw materials that remain viable but which the Company does not expect to sell within the next year.

Rental Equipment and Property and Equipment

Rental equipment and property and equipment are recorded at cost less accumulated depreciation, except for work-in-progress on new rental equipment which is recorded at cost until it’s complete and added to the fleet. Depreciation is computed using the straight-line method over the estimated useful lives of the assets. Our rental equipment has an estimated useful life between 15 and 25 years, while our property and equipment has an estimate useful lives which range from 3 to 39 years. The majority of our property and equipment, including rental equipment, is a direct cost to generating revenue.

We assess the impairment of rental equipment and property and equipment whenever events or changes in circumstances indicate that the net recorded amount may not be recoverable. The following factors could trigger an impairment review: significant underperformance relative to historical or projected future cash flows; significant adverse changes in the extent or manner in which asset (or asset group) is being used or its condition, including a meaningful drop in fleet utilization over the prior four quarters; significant negative industry or company-specific trends or actions, including meaningful capital expenditure budget reductions by our major customers or other sizable exploration and production or midstream companies, as well as significant declines in oil and natural gas prices; legislative changes prohibiting us from leasing our units or flares; or poor general economic conditions. An impairment loss is recognized if the future undiscounted cash flows associated with the asset (or asset group) and the estimated fair value of the asset are less than the asset's carrying value.

Sales of equipment out of the rental fleet are included with sales revenue and cost of sales, while retirements of units are shown a separate operating expense. Gains and losses resulting from sales and dispositions of other property and equipment are included with other income. Maintenance and repairs are charged to cost of rentals as incurred.

Goodwill

Intangibles

At December 31, 2019 and 2018, NGS had intangible assets, which relate to developed technology and a trade name. Developed technology is amortized on a straight-line basis with a useful life of 20 years, with a weighted average remaining life of approximately five years as of December 31, 2019. NGS has an intangible asset related to the trade name of SCS which was acquired in our acquisition of Screw Compression Systems in January 2005. This asset is not being amortized as it has been deemed to have an indefinite life.

Our policy is to review intangibles that are being amortized for impairment when indicators of impairment are present. In addition, it is our policy to review indefinite-lived intangible assets for impairment annually or when indicators of impairment are present. We review intangibles through an assessment of the estimated future cash flows related to such assets. In the event that assets are found to be carried at amounts in excess of estimated undiscounted future cash flows, then the assets will be adjusted for impairment to a level commensurate with a discounted cash flow analysis of the underlying assets.

Warranty

We accrue amounts for estimated warranty claims based upon current and historical product warranty costs and any other related information known. The warranty reserve was $74,000 and $22,000 for December 31, 2019 and 2018, respectively, and is included in accrued liabilities on the consolidated balance sheet.

Income Taxes

Deferred tax assets and liabilities are recognized for the future tax consequences attributable to temporary differences between the financial statement carrying amounts of assets and liabilities and their respective tax bases, and operating losses and tax credit carry-forwards. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. We assess the likelihood that our deferred tax assets will be recovered from future taxable income and, to the extent we believe that recovery is not probable, we establish a valuation allowance. To the extent we establish a valuation allowance or increase this allowance in a period, we include an expense in the tax provision in the statement of income.

ASC Topic 740 prescribes a recognition threshold and measurement attribute for the financial statement recognition and measurement of a tax position taken or expected to be taken in a tax return. In order to record any financial statement benefit, we are required to determine, based on technical merits of the position, whether it is more likely than not (a likelihood of more than 50 percent) that a tax position will be sustained upon examination, including resolution of any related appeals or litigation processes. If that step is satisfied, then we must measure the tax position to determine the amount of benefit to recognize in the financial statements. The tax position is measured at the largest amount of the benefit that is greater than 50 percent likely of being realized upon ultimate settlement.

Our policy regarding income tax interest and penalties is to expense those items as other expense.

We account for uncertain tax positions in accordance with guidance in FASB ASC 740, which prescribes the minimum recognition threshold a tax position taken or expected to be taken in a tax return is required to meet before being recognized in the financial statements. We have no uncertain tax positions as of December 31, 2019.

Fair Value Measurement

Fair value is defined as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date under current market conditions. ASC Topic 820 established a fair value hierarchy, which requires an entity to maximize the use of observable inputs when measuring fair value. These inputs are categorized as follows:

Level 1- quoted prices in an active market for identical assets or liabilities;

Level 2- quoted prices in an active market for similar assets or liabilities, inputs other than quoted prices that are observable for similar assets or liabilities, inputs derived principally from or corroborated by observable market data by correlation or other means; and

Level 3- valuation methodology with unobservable inputs that are significant to the fair value measurement.

Management believes that the fair value of our cash and cash equivalents, trade receivables, accounts payable and line of credit at December 31, 2019 and 2018 approximate their carrying values due to the short-term nature of the instruments or the use of prevailing market interest rates.

Segments and Related Information

ASC 280-10-50, “Operating Segments”, define the characteristics of an operating segment as a) being engaged in business activity from which it may earn revenue and incur expenses, b) being reviewed by the company's chief operating decision maker (CODM) for decisions about resources to be allocated and assess its performance and c) having discrete financial information. Although we indeed look at our products to analyze the nature of our revenue, other financial information, such as certain costs and expenses, net income and EBITDA are not captured or analyzed by these categories. Our CODM does not make resource allocation decisions or access the performance of the business based on these categories, but rather in the aggregate. Based on this, management believes that it operates in one business segment.

In their analysis of product lines as potential operating segments, management also considered ASC 280-10-50-11, “Aggregation Criteria”, which allows for the aggregation of operating segments if the segments have similar economic characteristics and if the segments are similar in each of the following areas:

•The nature of the products and services;

•The nature of the production processes;

•The type or class of customer for their products and services;

•The methods used to distribute their products or provide their services; and

•The nature of the regulatory environment, if applicable.

We are engaged in the business of designing and manufacturing compressors and flares. Our compressors and flares are sold and rented to our customers. In addition, we provide service and maintenance on compressors in our fleet and to third parties. These business activities are similar in all geographic areas. Our manufacturing process is essentially the same for the entire Company and is performed in house at our facilities in Midland, Texas and Tulsa, Oklahoma. Our customers primarily consist of entities in the business of producing natural gas. The maintenance and service of our products is consistent across the entire Company and is performed via an internal fleet of vehicles. The regulatory environment is similar in every jurisdiction in that the most impacting regulations and practices are the result of federal energy policy. In addition, the economic characteristics of each customer arrangement are similar in that we maintain policies at the corporate level.

Recently Issued Accounting Pronouncements

On January 1, 2019, the Company adopted ASC Topic 842, Leases. We applied certain practical expedients that allow companies to not reassess leases that are in effect prior to adoption, the practical expedient that allows lessors to not separate lease and non-lease components for certain asset classes and the practical expedient that allows lessors to exclude third party taxes from lease revenue and lease-related expenses. Adoption of ASC 842 resulted in an increase in lease assets and lease liabilities on the consolidated balance sheet of approximately $451,000. The adoption by the Company of ASC 842, in regards

to the increase in liabilities, did not impact the debt covenants on our existing line of credit, as leases are not considered new indebtedness in our credit agreement as confirmed with our bank.

In December 2019, the FASB issued ASU 2019-12, Income Taxes (ASC Topic 740), which simplifies accounting for income taxes by removing certain exceptions to various tax accounting principles and clarifies other existing guidance in order to improve consistency of application. These amendments are effective for public entities for interim and annual periods beginning after December 15, 2020. We are currently evaluating the impact of ASU 2019-12 on our consolidated financial statements and note disclosures.

In June 2016, the FASB issued ASU 2016-13, Financial Instruments-Credit Losses (ASC Topic 326): Measurement of Credit Losses on Financial Instruments. The amendments to ASC Topic 326 require immediate recognition of estimated credit losses expected to occur over the remaining life of many financial assets, including trade receivables. For companies that qualify as smaller reporting companies, the amendments in this update are effective for interim and annual periods beginning after January 1, 2023. We are currently evaluating the impact of ASU 2016-13 on our consolidated financial statements and note disclosures.

Revisions of Prior Period Financial Statements

In conjunction with the preparation of its year-end financial statements for 2019, the Company determined that certain, immaterial operating costs and expenses were inappropriately capitalized during the years ended December 31, 2018 and 2017, as well for interim periods in 2019 and 2018. As a result, the Company revised its prior period financial statements to incorporate additional operating costs and expenses of $1.1 million, $1.14 million and $96,000 for the nine months ended September 30, 2019, the year ended December 31, 2018 and the year ended December 31, 2017, respectively.

In accordance with Staff Accounting Bulletin (“SAB”) No. 99, “Materiality”, and SAB No. 108, “Considering the Effects of Prior Year Misstatements when Quantifying Misstatements in Current Year Financial Statements”, we evaluated the aforementioned errors and, based on an analysis of quantitative and qualitative factors, determined that the related impact was not material to our consolidated financial statements for any prior annual or interim period. Therefore, amendments of previously filed reports are not required. A summary of the revisions to our previously issued annual financial statements is included in Note 18, Revisions of Prior Period Financial Statements. In addition, a summary of the revisions to our unaudited quarterly financial data is included in Note 17, Quarterly Financial Data (Unaudited). The impacted balances in the accompanying notes to these consolidated financial statements have also been revised accordingly.

Inventory

12 Months Ended

Dec. 31, 2019

Inventory Disclosure [Abstract]

Inventory

Our inventory, net of allowance for obsolescence of $24,000 and $19,000 at December 31, 2019 and 2018, respectively, consisted of the following (in thousands):


	2019		2018
Raw materials - current	$	19,388	$	26,152
Work-in-process	1,692		3,016
Finished goods	—		1,022
Inventory - current	21,080		30,190
Raw materials - long term (net of allowances of $24 and $19, respectively	1,068		3,980
Inventory - total	$	22,148	$	34,170

There were seven newly completed compressor units available for sale in finished goods for a total of $1.0 million at December 31, 2018. These units were transferred from inventory to our rental fleet due to customer demands during 2019. In addition, our long-term inventory consists of raw materials that remain viable but which the Company does not expect to sell within the next year.

Inventory Allowance

Given its concerns about the industry backdrop, Company management determined during the third quarter of 2019 that an increase of its inventory allowance was necessary. Due to the slow moving nature or obsolescence of a portion of its long-term inventory and inventory related to the retirement of rental equipment, management recorded an increase of $3.4 million to the Company's inventory allowance reserve for costs that may not be recoverable in the future. During the

fourth quarter of 2019, management identified another $408,000 of slow moving or obsolete inventory. For the year ended December 31, 2019, inventory allowance totaled $3.8 million. We ended 2019 with an inventory allowance balance of $24,000.

A summary of our inventory allowance is as follows:


	Year Ended December 31,
($ in thousands)	2019		2018		2017
Beginning balance	$	(19)	$	(15)	$	(15)
Accruals	(3,758)		(4)		(273)
Write-offs	3,753		—		273
Ending balance	(24)		(19)		(15)

Rental Equipment, Property and Equipment

12 Months Ended

Dec. 31, 2019

Property, Plant and Equipment [Abstract]

Rental Equipment, Property and Equipment

Rental Equipment

Our rental equipment and associated accumulated depreciation as of December 31, 2019 and 2018, respectively, consisted of the following (in thousands):


	2019		2018
Compressor units	$	370,961	$	329,697
Work-in-progress	9,129		11,868
Rental equipment	380,090		341,565
Accumulated depreciation	(162,348)		(165,459)
Rental equipment, net of accumulated depreciation	$	217,742	$	176,106

Our rental equipment has an estimated useful life between 15 and 25 years. Depreciation expense for rental equipment was $21.4 million, $20.9 million and $20.0 million for the year ended December 31, 2019, 2018 and 2017, respectively.

In January 2019, the Company reviewed the estimated useful lives of its rental equipment. This review indicated that the actual lives of its larger horsepower rental equipment were longer than the estimated useful lives used for depreciation purposes in the Company’s financial statements. These units incorporate newer technology and heavier, more robust castings and forging, which allows for complete overhauls at longer cycles when compared to its older, lower horsepower units. Accordingly, as of January 1, 2019, the Company changed its estimates of the useful lives of for these higher horsepower units from 15 years to 20 years (for its 400-600 horsepower units) or 25 years (for its 1,380 horsepower units). This analysis is consistent with our peers, which are depreciating their compressor units over 20 to 30 years. The effect of this change in estimate was to reduce 2019 depreciation expense by approximately $1.47 million, decrease 2019 net loss by $1.13 million, and decrease 2019 basic and diluted loss per share by $0.09.

Retirement of Rental Equipment

Given its concerns about the current industry backdrop, Company management determined during the third quarter of 2019 which units were not of the type, configuration, make or model that our customers are demanding or that were not cost efficient to refurbish, maintain and/or operate. As a result of this review, we determined 327 units should be retired from our rental fleet. Accordingly, we recorded a $1.5 million loss on retirement of rental equipment during the year ended December 31, 2019.

During our review of our rental compressor units in 2018, we determined 13 units should be retired from our rental fleet. We recorded no loss on this retirement, as these units were fully depreciated. We did not record any retirements from our rental fleet in 2017.

Property and Equipment

Property and equipment consists of the following at December 31, 2019 and 2018 (in thousands):


	Useful Lives (Years)	2019		2018
Land	—	$	1,290	$	1,290
Building	39	18,632		6,116
Building and leasehold improvements	39	1,168		808
Office equipment and furniture	5	2,001		1,492
Software	5	573		573
Machinery and equipment	7	3,492		3,324
Vehicles	3	7,560		6,292
Construction in Progress	—	—		8,319
Total		34,716		28,214
Less accumulated depreciation		(12,847)		(11,570)
Total		$	21,869	$	16,644

Depreciation expense for property and equipment was $1.7 million, $1.1 million and $1.2 million for the year ended December 31, 2019, 2018 and 2017, respectively.

Depreciation Expense by Product Line

The following table depicts annual depreciation expense associated with each product line as well as our corporate activities at December 31, 2019, 2018 and 2017 (in thousands):


	2019		2018		2017
Rentals	$	22,596	$	21,611	$	20,873
Sales	275		271		267
Service & Maintenance	37		22		22
Corporate	235		50		29
Total	$	23,143	$	21,954	$	21,191

Leases

12 Months Ended

Dec. 31, 2019

Leases [Abstract]

Leases

The Company determines if an arrangement is a lease at inception by assessing whether it conveys the right to control the use of an identified asset for a period of time in exchange for consideration. The Company’s leases are primarily related to property leases for its field offices. The Company's leases have remaining lease terms of one to 10 years. Renewal and termination options are included in the lease term when it is reasonably certain that the Company will exercise the option.

The Company's lease agreements do not contain any contingent rental payments, material residual guarantees or material restrictive covenants.

ROU assets and lease liabilities are recognized at the lease commencement date based on the present value of lease payments over the lease term. As substantially all of the Company's leases do not provide an implicit rate, the Company uses its incremental borrowing rate, which is based on a fully collateralized loan over the lease term, to determine the present value of lease payments. Based on the present value of lease payments for the Company's existing leases, the Company recorded net lease assets and lease liabilities of approximately $451,000, respectively, upon adoption. The Company had no finance leases. The new lease standard did not materially impact the Company's consolidated statements of income and had no impact on the Company's consolidated statements of cash flows.

The impact of the new lease standard on the December 31, 2019 consolidated balance sheet was as follows:


	Classification on Consolidated Balance Sheet	December 31, 2019
		($ in thousands)
Operating lease assets	Right of use assets-operating leases	$	604

Current lease liabilities	Current operating leases	$	189
Noncurrent lease liabilities	Long-term operating leases	415
Total lease liabilities		$	604

Weighted average remaining lease term in years		2.6
Implicit Rate		3.1		%

Operating lease costs are recognized on a straight-line basis over the lease term. Total operating lease costs for the year ended December 31, 2019 was approximately $548,000.


	December 31, 2019
	(in thousands)
Cash paid for amounts included in the measurement of lease liabilities
Operating lease cost ^{(1) (2)}	$	548

(1) Lease costs are classified on the Consolidated Statements of Operations in cost of sales, cost of compressors and selling, general and administrative expenses.

(2) Includes costs of $350,000 for leases with terms of 12 months or less and $198,000 for leases with terms greater than 12 months.

The following table shows the future maturities of lease liabilities:


Years Ending December 31,	Lease Liabilities
	(in thousands)
2020	$	208
2021	172
2022	46
2023	38
2024	38
Thereafter	168
Total lease payments	670
Less: Imputed interest	(66)
Total	$	604

Under the previous lease standard (Topic 840), future minimum obligations under lease commitments in effect at December 31, 2018 were as follows:


	Operating Leases
	(in thousands)
2019	$	298
2020	118
2021	97
2022	44
2023	35
Thereafter	15
Total	$	607

Rent expense under such leases was $198,000, $433,000, and $310,000 for the years ended December 31, 2019, 2018 and 2017, respectively.

Goodwill

12 Months Ended

Dec. 31, 2019

Goodwill and Intangible Assets Disclosure [Abstract]

Goodwill

Goodwill represents the cost in excess of fair value of the identifiable net assets acquired. Goodwill is tested annually for impairment or as needed upon the occurrence of certain events or substantive changes in circumstances that indicate goodwill is more likely than not impaired. During the third quarter of 2019, the Company examined various qualitative factors to determine if a quantitative goodwill impairment test was needed. For several months prior to the end of the third quarter of 2019, the Company experienced a significant decline in stock price, which was reflective of the significant deterioration of stock prices of companies throughout the oilfield services sector. In addition, the Company noted its largest customer as well as several other exploration and production companies had announced significant reductions to their 2020 capital expenditures budgets compared to those in 2019. These reductions clearly indicated lower demand for oilfield services, including compression services, in 2020 compared to 2019. In addition, the reductions reflected the deteriorated equity markets for energy companies and demands from institutional investors that energy companies keep capital spending within operating cash flow. After considering these factors and various other industry, economic and company-specific factors, we calculated our market capitalization (based on our closing stock price) as of September 30, 2019, and compared it to the carrying value of our net assets. Since the carrying value of our net assets exceeded our market capitalization and after considering all of the aforementioned qualitative factors, Company management determined that it was more likely than not that the fair value of the Company’s net assets was less than its carrying amount.

As a result of our qualitative assessment, we proceeded to perform our quantitative goodwill impairment analysis, where we used an independent valuation specialist to assist us in determining the fair value of our net assets. In this impairment analysis, the estimated fair value of our net assets was determined utilizing market and income-based approaches. Determining fair value in this analysis required significant judgment, including judgments about appropriate comparable companies, appropriate discount rates and our estimated future cash flows, which are subject to change. As a result of our quantitative evaluation, we recorded a goodwill impairment charge of $10.0 million in 2019.


	Goodwill, net
December 31, 2018	$	10,039
Impairments	(10,039)
December 31, 2019	$	—

We experienced no impairment of goodwill during the years ended December 31, 2018 and 2017.

Intangibles

12 Months Ended

Dec. 31, 2019

Goodwill and Intangible Assets Disclosure [Abstract]

Intangibles

At December 31, 2019 and 2018, the Company had intangible assets, which relate to developed technology and a trade name. The carrying amount net of accumulated amortization at December 31, 2019 and 2018 was $1.3 million and $1.4 million, respectively. Amortization expense recognized in each of the years ending December 31, 2019, 2018, and 2017 was $125,000. Estimated amortization expense for the years 2020-2024 is $125,000 per year. The Company has an intangible asset with a gross carrying value of $654,000 at December 31, 2019 related to the trade name of SCS which was acquired in our acquisition of Screw Compression Systems in January 2005. This asset is not being amortized as it has been deemed to have an indefinite life.

The following table represents the identified intangible assets by major asset class (in thousands):


		December 31, 2019										December 31, 2018

	Useful Life (years)	Gross Carrying Value		Accumulated Amortization		Net Book Value		Gross Carrying Value		Accumulated Amortization		Net Book Value



Developed Technology	20	$	2,505	$	1,883	$	622	$	2,505	$	1,758	$	747
Trade Name	Indefinite	654		—		654		654		—		654
Total		$	3,159	$	1,883	$	1,276	$	3,159	$	1,758	$	1,401

In addition, in conjunction with our quantitative assessment of goodwill, we used the services of an independent valuation specialist to assist us in determining the fair value of our trade name during the third quarter of 2019. In this impairment analysis, the estimated fair value of our trade name was determined utilizing an income-based approach that required significant judgment, including those about an appropriate royalty rate and discount rate. This analysis indicated no impairment of our trade name.

Credit Facility	12 Months Ended
Credit Facility	Dec. 31, 2019
Debt Disclosure [Abstract]
Credit Facility	Credit Facility We have a senior secured revolving credit agreement with JP Morgan Chase Bank, N.A (the "Amended Credit Agreement") aggregate commitment of $30 million, subject to collateral availability. We also have a right to request from the Lender, on an uncommitted basis, an increase of up to $20 million on the aggregate commitment (which could potentially increase the commitment amount to $50 million). . Borrowing Base. At any time before the maturity of the Amended Credit Agreement, we may draw, repay and re-borrow amounts available under the borrowing base up to the maximum aggregate availability discussed above. Generally, the borrowing base equals the sum of (a) 80% of our eligible accounts receivable plus (b) 50% of the book value of our eligible general inventory (not to exceed 50% of the commitment amount at the time) plus (c) 75% of the book value of our eligible equipment inventory. JPMorgan Chase Bank (the “Lender”) may adjust the borrowing base components if material deviations in the collateral are discovered in future audits of the collateral. We had $29.5 million borrowing base availability at December 31, 2019 under the terms of our Amended Credit Agreement. Interest and Fees. Under the terms of the Amended Credit Agreement, we have the option of selecting the applicable variable rate for each revolving loan, or portion thereof, of either (a) LIBOR multiplied by the Statutory Reserve Rate (as defined in the Amended Credit Agreement), with respect to this rate, for Eurocurrency funding, plus the Applicable Margin (“LIBOR-based”), or (b) CB Floating Rate, which is the Lender's Prime Rate less the Applicable Margin; provided, however, that no more than three LIBOR-based borrowings under the agreement may be outstanding at any one time. For purposes of the LIBOR-based interest rate, the Applicable Margin is 1.50%. For purposes of the CB Floating Rate, the Applicable Margin is 1.25%. Accrued interest is payable monthly on outstanding principal amounts, provided that accrued interest on LIBOR-based loans is payable at the end of each interest period, but in no event less frequently than quarterly. In addition, fees and expenses are payable in connection with our requests for letters of credit (generally equal to the Applicable Margin for LIBOR-related borrowings multiplied by the face amount of the requested letter of credit) and administrative and legal costs. Maturity . The maturity date of the Amended Credit Agreement is December 31, 2020, at which time all amounts borrowed under the agreement will be due and outstanding letters of credit must be cash collateralized. The agreement may be terminated early upon our request or the occurrence of an event of default. Security. The obligations under the Amended Credit Agreement are secured by a first priority lien on all of our inventory and accounts and lease receivables, along with a first priority lien on a variable number of our leased compressor equipment the book value of must be maintained at a minimum of 2.00 to 1.00 commitment coverage ratio (such ratio being equal to (i) the amount of the borrowing base as of such date to (ii) the amount of the commitment as of such date.) Covenants. The Amended Credit Agreement contains customary representations and warranties, as well as covenants which, among other things, limit our ability to incur additional indebtedness and liens; enter into transactions with affiliates; make acquisitions in excess of certain amounts; pay dividends; redeem or repurchase capital stock or senior notes; make investments or loans; make negative pledges; consolidate, merge or effect asset sales; or change the nature of our business. In addition, we also have certain financial covenants that require us to maintain a leverage ratio less than or equal to 2.50 to 1.00 as of the last day of each fiscal quarter. Events of Default and Acceleration. The Amended Credit Agreement contains customary events of default for credit facilities of this size and type, and includes, without limitation, payment defaults; defaults in performance of covenants or other agreements contained in the loan documents; inaccuracies in representations and warranties; certain defaults, termination events or similar events; certain defaults with respect to any other Company indebtedness in excess of $50,000; certain bankruptcy or insolvency events; the rendering of certain judgments in excess of $150,000; certain ERISA events; certain change in control events and the defectiveness of any liens under the secured revolving credit facility. Obligations under the Amended Credit Agreement may be accelerated upon the occurrence of an event of default. As of December 31, 2019, we were in compliance with all covenants in our Amended Credit Agreement. A default under our Credit Agreement could trigger the acceleration of our bank debt so that it is immediately due and payable. Such default would likely limit our ability to access other credit. At December 31, 2019 our balance on the line of credit was $417,000. Our weighted average interest rate for the year ended December 31, 2019 was 3.06%.

Income Taxes

12 Months Ended

Dec. 31, 2019

Income Tax Disclosure [Abstract]

Income Taxes

The (provision for) benefit from income taxes for the years ended December 31, 2019, 2018 and 2017, consists of the following (in thousands):


	2019		2018		2017
Current benefit (provision):
Federal benefit (expense)	$	86	$	164	$	(3,031)
State (expense) benefit	(55)		78		(257)
Total current benefit (provision)	31		242		(3,288)
Deferred benefit (provision):
Federal benefit (expense)	662		(314)		21,575

Total deferred benefit (expense)	662		(314)		21,575
Total benefit (provision)	$	693	$	(72)	$	18,287

On December 22, 2017, the U.S. government enacted the 2017 Tax Act. The 2017 Tax Act made broad and complex changes to the U.S. tax code that affected the Company’s 2017 financial results. The 2017 Tax Act also established new tax laws that affected the Company’s financial results after 2017, including a reduction in the U.S. federal corporate income tax rate from 35 percent to 21 percent, additional limitations on the deductibility of executive compensation, limitations on the

deductibility of interest, and repeal of the domestic manufacturing deduction. As such, the Company recognized a $18.4 million income tax benefit related to the re-measurement of our deferred tax assets and liabilities in our 2017 financial statements in accordance with SAB 118, which provides SEC staff guidance for the application of ASC 740 in the reporting period in which the 2017 Tax Act was signed into law. We completed our detailed analysis in 2018 with no material adjustments.

The income tax effects of temporary differences that give rise to significant portions of deferred income tax assets and (liabilities) as of December 31, 2019 and 2018, are as follows (in thousands):


	2019		2018
Deferred income tax assets:
Net operating loss carryover	$	1,519	$	2,730
Stock compensation	580		746
Deferred compensation	$	389	$	243
Other	321		197
Total deferred income tax assets	$	2,809	$	3,916

Deferred income tax liabilities:
Property and equipment	$	(33,761)	(35,030)
Goodwill and other intangible assets	(291)		(573)
Other	—		(219)
Total deferred income tax liabilities	(34,052)		(35,822)
Net deferred income tax liabilities	$	(31,243)	$	(31,906)

The effective tax rate for the years ended December 31, 2019, 2018 and 2017, differs from the statutory rate as follows:


	2019		2018		2017
Statutory rate	21.0	%	21.0	%	34.0	%
State and local taxes	(3.7)	%	1.5	%	1.5	%
Uncertain tax position	—	%	(139.1)	%	—	%
Goodwill impairment	(13.7)	%	—	%	—	%
Research and development credit	1.4	%	92.2	%	—	%
Stock based compensation	(0.8)	%	10.0	%	(14.3)	%
Nondeductible compensation	(0.3)	%	(7.8)	%	—	%
Domestic production credit	—	%	—	%	(15.2)	%

Other	0.9	%	3.9	%	(1.5)	%
Effective rate	4.8	%	(18.3)	%	4.5	%
Deferred re-measurement for rate change	—	%	—	%	(1218.0)	%
Effective rate	4.8	%	(18.3)	%	(1213.5)	%

During the fourth quarter of 2018, the Company discovered a potential uncertain tax position attributable to the deductibility of certain executive compensation expense for federal income tax purposes aggregating approximately $168,000, $149,000 and $230,000 for the years ended December 31, 2017, 2016 and 2015, respectively. As a result, in accordance with ASC Topic 740, during the fourth quarter of 2018, the Company recorded a tax adjustment of $547,000 and accrued penalty and interest expense of $55,000 attributable to the uncertain tax position. Management of the Company determined that effect of the potential uncertain tax position on previously reported results of operations for the years ended December 31, 2017, 2016 and 2015 was not material.

As of December 31, 2019, the Company has filed amended tax returns for the years ended 2015, 2016 and 2017 and has recognized certain offsetting deductions, thus removing our uncertain tax position reserve for 2015, 2016 and 2017.

A reconciliation of the beginning and ending amount of uncertain tax positions is as follows (in thousands):


Balance at January 1, 2019	$	578
Additions based on tax positions related to current year	—
Reductions for tax positions of prior years	(578)


Balance at December 31, 2019	$	—

Our policy regarding income tax interest and penalties is to expense those items as incurred. During the years ended December 31, 2019, 2018 and 2017, there were no significant income tax interest or penalty items in the statement of income.

We had a regular income tax net operating loss carry forward of $6.7 million for federal income taxes as of December 31, 2019. This net operating loss will be carried forward indefinitely but subject to 80% limitation.

We file income tax returns in the U.S. federal jurisdiction and various state jurisdictions. With few exceptions, we are no longer subject to U.S. federal or state income tax examination by tax authorities for years before 2015.

Deferred Compensation Plans	12 Months Ended
Deferred Compensation Plans	Dec. 31, 2019
Compensation Related Costs [Abstract]
Deferred Compensation Plans	Deferred Compensation Plans Effective January 1, 2016, the Company established a non-qualified deferred compensation plan for executive officers, directors and certain eligible employees. The assets of the deferred compensation plan are held in a rabbi trust and are subject to additional risk of loss in the event of bankruptcy or insolvency of the Company. The plan allows for deferral up to 90% of a participant’s base salary, bonus, commissions, director fees and restricted stock awards. A Company owned life insurance policy held in a rabbi trust is utilized as a source of funding for the plan. The cash surrender value of the life insurance policy is $1.5 million and $1.0 million as of December 31, 2019 and 2018, respectively, with a gain related to the policy of $218,800 and a loss of $153,900 reported in other income in our consolidated income statement for the year ended December 31, 2019 and 2018, respectively. For deferrals of base salary, bonus, commissions and director fees, settlement payments are made to participants in cash, either in a lump sum or in periodic installments. The deferred obligation to pay the deferred compensation and the deferred director fees is adjusted to reflect the positive or negative performance of investment measurement options selected by each participant and was $1.7 million and $1.1 million as of December 31, 2019 and 2018, respectively. The deferred obligation is included in other long-term liabilities in the consolidated balance sheet. For deferrals of restricted stock units, the plan does not allow for diversification, therefore, distributions are paid in shares of common stock and the obligation is carried at grant value. As of December 31, 2019 and 2018, respectively, we have 85,565 and 101,895 unvested restricted stock units being deferred. As of December 31, 2019 and 2018, respectively we have released and issued 89,187 and 34,732 shares to the deferred compensation plan with a value of $1.7 million and $871,300, respectively.

Stockholders' Equity	12 Months Ended
Stockholders' Equity	Dec. 31, 2019
Stockholders' Equity Attributable to Parent [Abstract]
Stockholders' Equity	Stockholders' Equity Preferred Stock We have a total of 5.0 million authorized preferred shares with rights and preferences as designated by the Board of Directors. As of December 31, 2019 and 2018, there were no issued or outstanding preferred shares.

Rental Activity

12 Months Ended

Dec. 31, 2019

Leases [Abstract]

Rental Activity

Rental ActivityWe rent natural gas compressor packages to entities in the petroleum industry. These rental arrangements are classified as operating leases and generally have original terms of six months to sixty months and continue on a month-to-month basis thereafter.

Future minimum rent payments for arrangements not on a month-to-month basis at December 31, 2019 are as follows:


Years Ending December 31,
(in thousands)
2020	$	25,924
2021	$	18,489
2022	$	16,310
2023	$	12,507
2024	$	9,788
Thereafter	$	2,366
Total	$	85,384

Stock-Based Compensation

12 Months Ended

Dec. 31, 2019

Share-based Payment Arrangement [Abstract]

Stock-Based Compensation

Restricted Stock/Units

On June 18, 2014, at our annual meeting of shareholders, our shareholders approved a proposed amendment to the 2009 Restricted Stock/Unit Plan (the "2009 Plan") to add additional 500,000 shares of common stock to the Plan, thereby authorizing the issuance of up to 800,000 shares of common stock under the Plan. The 2009 Plan expired on June 16, 2019. At December 31, 2019 we had 123,092 shares outstanding under the 2009 Plan that will vest over the next two years.

On June 20, 2019, at our annual meeting of shareholders, our shareholders approved a new proposed Equity Incentive Plan for restricted shares/units and stock options. The Equity Incentive Plan allows issuance up to 500,000 share of common stock. As to December 31, 2019, only restricted shares/units had been granted.

In accordance with the Company's employment agreement with Stephen Taylor, the Company's Chief Executive Officer, the Compensation Committee reviewed his performance in determining the issuance of restricted common stock. Based on this review which included consideration of the Company's 2018 performance, Mr. Taylor, was awarded 131,674 restricted shares/units on March 29, 2019, which vest over three years, in equal installments beginning March 29, 2020. On March 29, 2019, the Compensation Committee awarded 20,000 restricted shares/units to each G. Larry Lawrence, our former CFO, and James Hazlett, our Vice President of Technical Services. The restricted shares/units to Messrs. Hazlett and G.L. Lawrence vest over three years, in equal installments, beginning March 29, 2020. We also awarded and issued 23,136 shares of restricted common stock/units to our Board of Directors as partial payment for 2019 directors' fees. The restricted stock/units issued to our directors vests over one year, in quarterly installments, beginning March 31, 2020.

On November 15, 2019, our former CFO, G. Larry Lawrence, retired from the Company. At time of retirement, the Board of Directors approved the accelerated vesting of all unvested shares held by Mr. Lawrence. In accordance with ASC 718, the Company considered the Board’s approval of accelerated vesting as a modification to all of the unvested shares held by Mr. Lawrence on the date of his retirement. The grant-date fair value of Mr. Lawrence’s restricted shares/units ranged from $17.29 to $24.55 per share. The closing price of the Company's stock was $11.18 on November 15, 2019, the modification date. Due to the price on date of modification being less than the original grant value, the Company recorded less compensation expense related to the accelerated vesting than would have been recognized over the vesting period if Mr. Lawrence had not retired. Total compensation expensed booked related to the Mr. Lawrence’s accelerated shares was $189,000.

Compensation expense related to the restricted shares/units was approximately $2.5 million, $2.2 million and $3.7 million for the years ended December 31, 2019, 2018, and 2017, respectively. As of December 31, 2019, there was a total of approximately $3.3 million of unrecognized compensation expense related to the nonvested portion of these restricted shares/units. This expense is expected to be recognized over the next three years and a quarter. As of December 31, 2019, 328,173 shares were still available for issuance under the Equity Incentive Plan.

A summary of all restricted stock/units activity as of December 31, 2017, 2018 and 2019 and changes during the years then ended are presented below.


	Number of Shares	Weighted Average Exercise Price		Weighted Average Remaining Contractual Life (years)	Aggregate Intrinsic Value (in thousands)
Outstanding, December 31, 2016	139,451	$	21.34	9.13	$	4,483
Granted	126,432	27.06		—	3,421
Vested	(81,494)	21.20		—	2,361
Canceled/Forfeited	—	—		—	—
Outstanding, December 31, 2017	184,389	$	25.32	8.83	$	4,831
Granted	140,988	24.55		—	3,461
Vested	(110,747)	23.97		—	2,806
Canceled/Forfeited	—	—		—	—
Outstanding, December 31, 2018	214,630	$	25.51	8.85	$	3,529
Granted	199,810	17.16		—	3,433
Vested	(134,674)	24.26		—	2,807
Canceled/Forfeited	—	—		—	—
Outstanding, December 31, 2019	279,766	$	20.15	8.77	$	3,430

Stock Option Plan

Our Stock Option Plan which is stockholder approved, permits the granting of stock options to its employees for up to 1.0 million shares of common stock under the Stock Option Plan. We believe that such awards align the interests of our employees with our stockholders. Option awards are generally granted with an exercise price equal to the market price of our stock at the date of grant; those option awards generally vest based on three years of continuous service and have ten-year contractual terms. Certain option and share awards provide for accelerated vesting if there is a change in control of the Company (as defined in the Stock Option Plan). The last date that grants can be made under the Stock Option Plan is February 28, 2026. As of December 31, 2019, 337,503 shares were still available for issue under the Stock Option Plan.

The fair value of each option award is estimated on the date of grant using the Black-Scholes option valuation model that uses the assumptions noted in the following table. The risk-free rate for periods within the contractual life of the option is based on the U.S. Treasury yield curve in effect at the time of grant. The expected life of options granted is based on the vesting period and historical exercise and post-vesting employment termination behavior for similar grants. We use historical data to estimate option exercise and employee termination within the valuation model; separate groups of employees that have similar historical exercise behavior are considered separately for valuation purposes.


Weighted average Black -Scholes fair value assumption during the year ended December 31, are as follows:	2017
Risk free rate	2.12	%
Expected life	6 years
Expected volatility	39.59	%
Expected dividend yield	—

There were no stock option grants made in 2019 or 2018.

A summary of all option activity as of December 31, 2017, 2018 and 2019 and changes during the years then ended are presented below:


	Number of Shares	Weighted Average Grant Date Fair Value		Weighted Average Remaining Contractual Life (years)	Aggregate Intrinsic Value (in thousands)
Outstanding, December 31, 2016	350,186	$	19.45	4.25	$	4,453
Granted	32,750	28.15		—	—
Exercised	(55,666)	20.12		—	446

Outstanding, December 31, 2017	327,270	$	20.21	4.28	$	2,255

Granted	—	—		—	—
Exercised	(38,250)	17.19		—	216
Canceled/Forfeited	(5,534)	24.02		—	—
Outstanding, December 31, 2018	283,686	$	20.46	3.58	$	434
Granted	—	—		—	—
Exercised	(56,352)	8.97		—	474
Canceled/Forfeited	(8,000)	21.60		—	—
Expired	(11,000)	17.74		—	—
Outstanding, December 31, 2019	208,334	$	23.67	3.66	$	—
Exercisable, December 31, 2019	197,901	$	23.43	3.48	$	—

The weighted average grant date fair value of options granted during 2017 was $11.93. We had no grants in 2019 and in 2018. The total intrinsic value, or the difference between the exercise price and the market price on the date of exercise, of options exercised during the years ended December 31, 2019, 2018, and 2017 was approximately $474,000, $216,000, and $446,000, respectively. Cash received from stock options exercised during the years ended December 31, 2019, 2018, and 2017 was approximately $506,000, $680,000, and $1.1 million, respectively.

The following table summarizes information about our stock options outstanding at December 31, 2019:


Range of Exercise Prices	Options Outstanding												Options Exercisable
		Shares		Weighted Average Remaining Contractual Life (years)			Weighted Average Exercise Price		Shares			Weighted Average Exercise Price

$0.01-15.70	8,500		2.07		$	14.89		8,500		$	14.89
$15.71-17.81	26,000		0.74		17.40			26,000		17.40
$17.82-20.48	50,500		1.34		19.43			50,500		19.43
$20.49-33.36	123,334		5.34		27.33			112,901		27.26
	208,334		3.66		$	23.67		197,901		$	23.43

The summary of the status of our unvested stock options as of December 31, 2019 and changes during the year then ended is presented below.


Unvested stock options:	Shares	Weighted Average Grant Date Fair Value
Unvested at December 31, 2018	20,865	$	11.93
Granted	—	—
Vested	(10,432)	11.93
Canceled/Forfeited	—	—
Unvested at December 31, 2019	10,433	$	11.93

We recognized stock compensation expense from stock options vesting of $124,000, $159,000, and $363,000 for the years ended December 31, 2019, 2018 and 2017, respectively. As of December 31, 2019, there was approximately $16,000 of total unamortized compensation cost related to unvested stock options. We expect to recognize such cost in 2020.

(Loss) Earnings per Share

12 Months Ended

Dec. 31, 2019

Earnings Per Share [Abstract]

(Loss) Earnings per Share

Basic (loss) earnings per common share is computed using the weighted average number of common shares outstanding during the period. Diluted (loss) earnings per common share is computed using the weighted average number of common stock and common stock equivalent shares outstanding during the period.

The following table sets forth the computation of basic and diluted (loss) earnings per share (in thousands, except per share amounts):


	Year Ended December 31,
	2019		2018		2017
Numerator:
Net (loss) income	$	(13,864)	$	(466)	$	19,794
Denominator for basic net (loss) income per common share:
Weighted average common shares outstanding	13,114		12,965		12,831
Denominator for diluted net (loss) income per share:
Weighted average common shares outstanding	13,114		12,965		12,831
Dilutive effect of stock options and restricted shares	—		—		279
Diluted weighted average shares	13,114		12,965		13,110
(Loss) earnings per common share:
Basic	$	(1.06)	$	(0.04)	$	1.54
Diluted	$	(1.06)	$	(0.04)	$	1.51

In the years ended ended December 31, 2019 and 2018, restricted stock and stock options were not included in the computation of diluted loss per share due to their antidilutive effect.

In the year-ended December 31, 2017, options to purchase 83,917 shares of common stock with exercise prices ranging from $28.15 to $33.36 were not included in the computation of dilutive income per share, due to their anti-dilutive effect.

Related Party	12 Months Ended
Related Party	Dec. 31, 2019
Related Party Transactions [Abstract]
Related Party	Related Party In 2016, we entered into a joint venture partnership, N-G, LLC (‘N-G”), with Genis Holdings, LLC (“Genis”) to explore new technologies for wellhead compression. NGS and Genis both share 50% ownership of N-G. We account for this investment under the equity method. In 2018, we ordered some compressor packages from Genis, totaling $1.0 million. The compressors were completed and paid in full at December 31, 2019.

Commitments and Contingencies	12 Months Ended
Commitments and Contingencies	Dec. 31, 2019
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies 401(k) Plan We offer a 401(k) Plan to all employees that have reached the age of eighteen and have completed two months of service. The participants may contribute up to 100% of their salary subject to IRS limitations. Employer contributions are subject to Board discretion and are subject to a vesting schedule of 20% each year after the first year and 100% after six years. We contributed $393,000, $355,000, and $301,000 to the 401(k) Plan in 2019, 2018 and 2017, respectively, which is recorded in cost of revenues and selling, general and administrative expenses.. Legal Proceedings From time to time, we are a party to various legal proceedings in the ordinary course of our business. While management is unable to predict the ultimate outcome of these actions, it believes that any ultimate liability arising from these actions will not have a material effect on our financial position, results of operations or cash flow. We are not currently a party to any bankruptcy, receivership, reorganization, adjustment or similar proceeding, and we are not aware of any other threatened litigation.

Quarterly Financial Data - Unaudited

12 Months Ended

Dec. 31, 2019

Quarterly Financial Data [Abstract]

Quarterly Financial Data - Unaudited

Quarterly Financial Data (Unaudited)

The following tables presents selected unaudited financial data for each of the eight quarters in the two-year period ended December 31, 2019, which have been updated to reflect the revisions discussed in Note 2 (Summary of Significant Accounting Policies). The revisions to the Company's unaudited interim financial statements during 2019 will be incorporated when it issues its Forms 10-Q for the first three quarter of 2020.

The Company believes this information reflects all recurring adjustments necessary to fairly state this information when read in conjunction with the Company's financial statements and the related notes. Please note that amounts in the tables below may not sum due to rounding differences.

(in thousands, except per share)


2019	Q1		Q2		Q3		Q4		Total
Total revenue	$	17,991	$	19,895	$	20,852	$	19,706	$	78,444
Operating income (loss)	(145)		302		(14,021)		(1,289)		(15,153)
Net income (loss)	98		327		(12,579)		(1,710)		(13,864)
Earnings (loss) per share, basic	0.01		0.02		(0.96)		(0.13)		(1.06)
Earnings (loss) per share, diluted	0.01		0.02		(0.96)		(0.13)		(1.06)
Earnings (loss) per share, year to date, basic	0.01		0.03		(0.93)		(1.06)		(1.06)
Earnings (loss) per share, year to date, diluted	0.01		0.03		(0.93)		(1.06)		(1.06)


2018	Q1		Q2		Q3		Q4		Total
Total revenue	$	14,718	$	18,204	$	16,396	$	16,160	$	65,478
Operating income (loss)	305		179		(500)		(491)		(507)
Net income (loss)	190		211		(118)		(749)		(466)
Earnings (loss) per share, basic	0.01		0.02		(0.01)		(0.06)		(0.04)
Earnings (loss) per share, diluted	0.01		0.02		(0.01)		(0.06)		(0.04)

Revisions to our unaudited quarterly financial data are as follows:


	For the Three Months Ended September 30, 2019
($ in thousands, except per share)	As Reported		Revisions		As Revised
Total revenue	$	20,852	$	—	$	20,852
Operating loss	(13,561)		(460)		(14,021)
Net loss	(12,232)		(347)		(12,579)
Loss per share, basic	(0.93)		(0.03)		(0.96)
Loss per share, diluted	(0.93)		(0.03)		(0.96)


	For the Three Months Ended June 30, 2019
($ in thousands, except per share)	As Reported		Revisions		As Revised
Total revenue	$	19,895	$	—	$	19,895
Operating income (loss)	593		(291)		302
Net income (loss)	573		(246)		327
Earnings (loss) per share, basic	0.04		(0.02)		0.02
Earnings (loss) per share, diluted	0.04		(0.02)		0.02


	For the Three Months Ended March 31, 2019
($ in thousands, except per share)	As Reported		Revisions		As Revised
Total revenue	$	17,991	$	—	$	17,991
Operating income (loss)	209		(354)		(145)
Net income (loss)	357		(259)		98
Earnings (loss) per share, basic	0.03		(0.02)		0.01
Earnings (loss) per share, diluted	0.03		(0.02)		0.01


	For the Three Months Ended December 31, 2018
($ in thousands, except per share)	As Reported		Revisions		As Revised
Total revenue	$	16,160	$	—	$	16,160
Operating loss	106		(597)		(491)
Net loss	(282)		(467)		(749)
Loss per share, basic	(0.02)		(0.04)		(0.06)
Loss per share, diluted	(0.02)		(0.04)		(0.06)


	For the Three Months Ended September 30, 2018
($ in thousands, except per share)	As Reported		Revisions		As Revised
Total revenue	$	16,396	$	—	$	16,396
Operating (loss)	(44)		(456)		(500)
Net income (loss)	236		(354)		(118)
Earnings (loss) per share, basic	0.02		(0.03)		(0.01)
Earnings (loss) per share, diluted	0.02		(0.03)		(0.01)


	For the Three Months Ended June 30, 2018
($ in thousands, except per share)	As Reported		Revisions		As Revised
Total revenue	$	18,204	$	—	$	18,204
Operating income (loss)	226		(47)		179
Net income (loss)	247		(36)		211
Earnings (loss) per share, basic	0.02		—		0.02
Earnings (loss) per share, diluted	0.02		—		0.02


	For the Three Months Ended March 31, 2018
($ in thousands, except per share)	As Reported		Revisions		As Revised
Total revenue	$	14,718	$	—	$	14,718
Operating income (loss)	350		(45)		305
Net income (loss)	225		(35)		190
Earnings (loss) per share, basic	0.02		(0.01)		0.01
Earnings (loss) per share, diluted	0.02		(0.01)		0.01

Revisions of Prior Period Financial Statements

12 Months Ended

Dec. 31, 2019

Accounting Changes and Error Corrections [Abstract]

Revisions of Prior Period Financial Statements

As discussed in Note 2 (Summary of Significant Accounting Policies), in conjunction with the preparation of its year-end financial statements for 2019, the Company determined that certain, immaterial operating costs and expenses were inappropriately capitalized during the years ended December 31, 2018 and 2017, as well for interim periods in 2019 and 2018. As a result, the Company revised its prior period financial statements to incorporate additional operating costs and expenses of $1.1 million, $1.14 million and $96,000 for the nine months ended September 30, 2019, the year ended December 31, 2018 and the year ended December 31, 2017, respectively.

These revisions are summarized in the tables below.

Revised Consolidated Balance Sheet


	As of December 31, 2018
($ in thousands)	As Reported		Revisions		As Revised
Assets
Inventory	$	30,974	$	(784)	$	30,190
Prepaid income taxes	3,148		40		3,188
Prepaid expenses and other	2,430		(734)		1,696
Total current assets	96,399		(1,478)		94,921
Rental equipment, net of accumulated depreciation	175,886		220		176,106
Property and equipment, net of accumulated depreciation	16,587		57		16,644
Total assets	305,401		(1,201)		304,200

Liabilities and Stockholders' Equity
Deferred income tax liability	$	32,158	$	(252)	$	31,906
Total liabilities	45,220		(252)		44,968
Retained earnings	152,291		(949)		151,342
Total stockholders' equity	260,181		(949)		259,232
Total liabilities and stockholders' equity	305,401		(1,201)		304,200

Revised Consolidated Statements of Income


	For the Year Ended December 31, 2018
($ in thousands, except per share)	As Reported		Revisions		As Revised
Total revenue	$	65,478	$	—	$	65,478
Operating costs and expenses:
Cost of rentals, exclusive of depreciation stated separately below	20,746		1,114		21,860
Depreciation and amortization	22,049		31		22,080
Total operating costs and expenses	64,840		1,145		65,985
Operating income (loss)	638		(1,145)		(507)
Income (loss) before provision for income taxes	751		(1,145)		(394)
Provision for income taxes:
Current benefit (expense)	248		(6)		242
Deferred (expense) benefit	(573)		259		(314)
Income tax (expense) benefit	(325)		253		(72)
Net income (loss)	426		(892)		(466)
Earnings (loss) per share, basic	0.03		(0.07)		(0.04)
Earnings (loss) per share, diluted	0.03		(0.07)		(0.04)


	For the Year Ended December 31, 2017
($ in thousands, except per share)	As Reported		Revisions		As Revised
Total revenue	$	67,693	$	—	$	67,693
Operating costs and expenses:
Cost of rentals, exclusive of depreciation stated separately below	18,078		82		18,160
Depreciation and amortization	21,302		14		21,316
Total operating costs and expenses	66,126		96		66,222
Operating income (loss)	1,567		(96)		1,471
Income (loss) before provision for income taxes	1,603		(96)		1,507
Provision for income taxes:
Current (expense) benefit	(3,334)		46		(3,288)
Deferred benefit (expense)	21,582		(7)		21,575
Income tax benefit	18,248		39		18,287
Net income (loss)	19,851		(57)		19,794
Earnings (loss) per share, basic	1.55		(0.01)		1.54
Earnings (loss) per share, diluted	1.51		—		1.51

Revised Consolidated Statements of Stockholders' Equity


	For the Year Ended December 31, 2018
($ in thousands)	As Reported		Revisions		As Revised
Net income (loss)	$	426	$	(892)	$	(466)
Retained earnings	152,291		(949)		151,342
Total stockholders' equity	260,181		(949)		259,232


	For the Year Ended December 31, 2017
($ in thousands)	As Reported		Revisions		As Revised
Net income (loss)	$	19,851	$	(57)	$	19,794
Retained earnings	151,865		(57)		151,808
Total stockholders' equity	257,319		(57)		257,262

Revised Consolidated Statements of Cash Flows


	For the Year Ended December 31, 2018
($ in thousands)	As Reported		Revisions		As Revised
Cash flows from operating activities:
Net income (loss)	$	426	$	(892)	$	(466)
Depreciation and amortization	22,049		31		22,080
Deferred taxes	573		(259)		314
Inventory (increase) decrease	(5,757)		655		(5,102)
Prepaid income taxes and prepaid expenses (increase) decrease	(1,318)		740		(578)
Net cash provided by operating activities	23,414		275		23,689
Cash flows from investing activities:
Purchase of rental equipment, property and other equipment	(39,790)		(275)		(40,065)
Net cash used in investing activities	(40,010)		(275)		(40,285)
Net change in cash and cash equivalents	(16,580)		—		(16,580)


	For the Year Ended December 31, 2017
($ in thousands)	As Reported		Revisions		As Revised
Cash flows from operating activities:
Net income (loss)	$	19,851	$	(57)	$	19,794
Depreciation and amortization	21,302		14		21,316
Deferred taxes	(21,582)		7		(21,575)
Inventory (increase) decrease	(5,350)		129		(5,221)
Prepaid income taxes and prepaid expenses increase	(1,806)		(46)		(1,852)
Net cash provided by operating activities	17,452		47		17,499
Cash flows from investing activities:
Purchase of rental equipment, property and other equipment	(13,489)		(47)		(13,536)
Net cash used in investing activities	(12,791)		(47)		(12,838)
Net change in cash and cash equivalents	5,114		—		5,114

Subsequent Events	12 Months Ended
Subsequent Events	Dec. 31, 2019
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events On January 30, 2020, the World Health Organization (“WHO”) announced a global health emergency because of a new strain of coronavirus known as COVID-19 due to the risks it imposes on the international community as the virus spreads globally. In March 2020, the WHO classified the COVID-19 outbreak as a pandemic, based on the rapid increase in exposure globally. During this time, the market began to experience a decline in oil prices in response to oil demand concerns due to the global economic impacts of COVID-19. In addition, recent events concerning OPEC and Russia resulted in Saudi Arabia significantly discounting the price of its crude oil, as well as Saudi Arabia and Russia significantly increasing their oil supply. These actions have led to significant weakness in oil prices and ensuing reductions of exploration and production company capital and operating budgets. The full impact of the COVID-19 outbreak continues to evolve daily as of the date of this report. With the significant decline in oil prices as well as the general economic decline caused by the impacts of COVID-19, we expect utilization to decline among our smaller horsepower and medium horsepower units during the remainder of 2020 after a minimal decline during the first quarter of 2020. In terms of sales, we expect minimal compressor sales for the year due to much lower capital expenditure budgets throughout the industry, including those of our major customers. Finally, we have recently experienced and expect to continue to experience pricing pressure from our customers and competitors until industry and economic conditions improve. We are currently experiencing no issues with potential workforce and supply chain disruptions. Our relationship with our major customer continues to be strong, and they have continued to pay our invoices in a timely, consistent manner. Nevertheless, if any of these circumstances change, our business could be adversely affected. While management anticipates that the industry and economic impact of the pandemic and OPEC’s actions will have a negative effect on its results of operations in 2020 and perhaps beyond, the degree to which these factors will impact our business remains uncertain.

Summary of Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2019

Accounting Policies [Abstract]

Principles of Consolidation

Principles of ConsolidationThe accompanying consolidated financial statements include the accounts of the Company, its subsidiary, NGSG Properties, LLC and the rabbi trust associated with the Company’s deferred compensation plan, see Note 10. All significant intercompany accounts and transactions for the periods presented have been eliminated in consolidation.

Reclassifications

Certain prior year amounts have been reclassified to conform to the current year's presentation.

Use of Estimates

Cash Equivalents, Financial Instruments and Concentration of Credit Risks

Accounts Receivable

A summary of our allowance for doubtful accounts is as follows:


	Year Ended December 31,
($ in thousands)	2019		2018		2017
Beginning balance	$	(291)	$	(569)	$	(597)
Accruals	(664)		—		(90)
Recoveries	—		185		—
Write-offs	37		93		118
Ending balance	(918)		(291)		(569)

Revenue Recognition

Revenue Recognition Policy

Nature of Goods and Services

The following is a description of principal activities from which the Company generates its revenue:

Service and Maintenance Revenue. The Company provides routine or call-out services on customer owned equipment. Revenue is recognized after services in the contract are rendered.

Contract Costs

Leases

The cumulative effect of the changes made to our consolidated balance sheet at January 1, 2019, for the adoption of ASC 842 was as follows (in thousands):


	Balance at December 31, 2018		Adjustments due to ASC 842		Balance at January 1, 2019
Balance Sheet
Assets
Right of use assets	$	—	$	451	$	451
Liabilities
Current portion of operating leases	$	—	$	126	$	126
Long term portion of operating leases	—		325		325
Total lease liabilities	$	—	$	451	$	451

Major Customers and Concentration of Credit Risk

Major Customers and Concentration of Credit RiskSales and rental income from Occidental Permian, LTD. ("Oxy") in 2019 and 2018 amounted to 36% and 28% of revenue, respectively. Sales and rental income to Oxy and Devon Energy Production, Inc. in 2017 amounted to 20% and 15% of revenue, respectively. No other single customer accounted for more than 10% of our revenues in 2019, 2018 or 2017. Oxy's accounts receivable balances amounted to 35% and 26% of our accounts receivable as of December 31, 2019 and 2018, respectively. No other customers amounted to more than 10% of our accounts receivable as of December 31, 2019 and 2018.

Inventory

InventoryInventory (current and long-term) is valued at the lower of cost and net realizable value. The cost of inventories is determined by the weighted average method. We regularly review inventory quantities on hand and record a provision for excess and obsolete inventory based primarily on current and anticipated customer demand and production requirements. The Company accesses anticipated customer demand based on current and upcoming capital expenditure budgets of its major customers as well as other significant companies in the industry, along with oil and natural gas price forecasts and other factors affecting the industry. In addition, our long-term inventory consists of raw materials that remain viable but which the Company does not expect to sell within the next year.

Rental Equipment and Property and Equipment

Rental Equipment and Property and EquipmentRental equipment and property and equipment are recorded at cost less accumulated depreciation, except for work-in-progress on new rental equipment which is recorded at cost until it’s complete and added to the fleet. Depreciation is computed using the straight-line method over the estimated useful lives of the assets. Our rental equipment has an estimated useful life between 15 and 25 years, while our property and equipment has an estimate useful lives which range from 3 to 39 years. The majority of our property and equipment, including rental equipment, is a direct cost to generating revenue.

Impairment of Rental Equipment

Goodwill

GoodwillGoodwill represents the cost in excess of fair value of the identifiable net assets acquired. Goodwill is tested annually for impairment or as needed upon the occurrence of certain events or substantive changes in circumstances that indicate goodwill is more likely than not impaired. As further described in Note 6 of these financial statements, we fully impaired the Company's goodwill during the third quarter of 2019, resulting in a goodwill impairment charge of $10.0 million for the year ended December 31, 2019.

Intangibles

Warranty

WarrantyWe accrue amounts for estimated warranty claims based upon current and historical product warranty costs and any other related information known.

Income Taxes

Our policy regarding income tax interest and penalties is to expense those items as other expense.

Fair Value Measurement

Level 1- quoted prices in an active market for identical assets or liabilities;

Level 3- valuation methodology with unobservable inputs that are significant to the fair value measurement.

Segments and Related Information

•The nature of the products and services;

•The nature of the production processes;

•The type or class of customer for their products and services;

•The methods used to distribute their products or provide their services; and

•The nature of the regulatory environment, if applicable.

Recently Issued Accounting Pronouncements

to the increase in liabilities, did not impact the debt covenants on our existing line of credit, as leases are not considered new indebtedness in our credit agreement as confirmed with our bank.

Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2019

Accounting Policies [Abstract]

Schedule of Allowance for Doubtful Accounts

A summary of our allowance for doubtful accounts is as follows:


	Year Ended December 31,
($ in thousands)	2019		2018		2017
Beginning balance	$	(291)	$	(569)	$	(597)
Accruals	(664)		—		(90)
Recoveries	—		185		—
Write-offs	37		93		118
Ending balance	(918)		(291)		(569)

Disaggregation of Revenue

The following table shows the Company's revenue disaggregated by product or service type for the years ended:



	Year Ended December 31,
	(in thousands)
	2019		2018		2017
Compressors - sales	$	15,185	$	10,994	$	13,382
Flares - sales	959		2,535		2,755
Other (Parts/Rebuilds) - sales	3,619		2,740		4,071
Service and maintenance	1,980		1,443		1,439
Total revenue from contracts with customers	21,743		17,712		21,647
Add: ASC 842 rental revenue	56,701		47,766		46,046
Total revenue	$	78,444	$	65,478	$	67,693

Contract with Customer, Asset and Liability

As of December 31, 2019 and December 31, 2018, we had the following receivables and deferred income from contracts with customers:


	December 31, 2019		December 31, 2018
	(in thousands)
Accounts Receivable
Accounts receivable - contracts with customers	$	3,061	$	2,390
Accounts receivable - ASC 842	6,963		5,120
Total Accounts Receivable	10,024		7,510
Less: Allowance for doubtful accounts	(918)		(291)
Total Accounts Receivable, net	9,106		7,219

Deferred income	$	640	$	81

Cumulative Effect of Changes from Adoption of ASU

The cumulative effect of the changes made to our consolidated balance sheet at January 1, 2019, for the adoption of ASC 842 was as follows (in thousands):


	Balance at December 31, 2018		Adjustments due to ASC 842		Balance at January 1, 2019
Balance Sheet
Assets
Right of use assets	$	—	$	451	$	451
Liabilities
Current portion of operating leases	$	—	$	126	$	126
Long term portion of operating leases	—		325		325
Total lease liabilities	$	—	$	451	$	451

Schedule of Identified Finite-Lived Intangible Assets, Finite Lived

The following table represents the identified intangible assets by major asset class (in thousands):


		December 31, 2019										December 31, 2018

	Useful Life (years)	Gross Carrying Value		Accumulated Amortization		Net Book Value		Gross Carrying Value		Accumulated Amortization		Net Book Value



Developed Technology	20	$	2,505	$	1,883	$	622	$	2,505	$	1,758	$	747
Trade Name	Indefinite	654		—		654		654		—		654
Total		$	3,159	$	1,883	$	1,276	$	3,159	$	1,758	$	1,401

Schedule of Identified Indefinite-Lived Intangible Assets

The following table represents the identified intangible assets by major asset class (in thousands):


		December 31, 2019										December 31, 2018

	Useful Life (years)	Gross Carrying Value		Accumulated Amortization		Net Book Value		Gross Carrying Value		Accumulated Amortization		Net Book Value



Developed Technology	20	$	2,505	$	1,883	$	622	$	2,505	$	1,758	$	747
Trade Name	Indefinite	654		—		654		654		—		654
Total		$	3,159	$	1,883	$	1,276	$	3,159	$	1,758	$	1,401

Computation of Basic and Diluted Earnings Per Share

The following table sets forth the computation of basic and diluted (loss) earnings per share (in thousands, except per share amounts):


	Year Ended December 31,
	2019		2018		2017
Numerator:
Net (loss) income	$	(13,864)	$	(466)	$	19,794
Denominator for basic net (loss) income per common share:
Weighted average common shares outstanding	13,114		12,965		12,831
Denominator for diluted net (loss) income per share:
Weighted average common shares outstanding	13,114		12,965		12,831
Dilutive effect of stock options and restricted shares	—		—		279
Diluted weighted average shares	13,114		12,965		13,110
(Loss) earnings per common share:
Basic	$	(1.06)	$	(0.04)	$	1.54
Diluted	$	(1.06)	$	(0.04)	$	1.51

Inventory (Tables)

12 Months Ended

Dec. 31, 2019

Inventory Disclosure [Abstract]

Schedule of Inventory and Allowance

Our inventory, net of allowance for obsolescence of $24,000 and $19,000 at December 31, 2019 and 2018, respectively, consisted of the following (in thousands):


	2019		2018
Raw materials - current	$	19,388	$	26,152
Work-in-process	1,692		3,016
Finished goods	—		1,022
Inventory - current	21,080		30,190
Raw materials - long term (net of allowances of $24 and $19, respectively	1,068		3,980
Inventory - total	$	22,148	$	34,170

A summary of our inventory allowance is as follows:


	Year Ended December 31,
($ in thousands)	2019		2018		2017
Beginning balance	$	(19)	$	(15)	$	(15)
Accruals	(3,758)		(4)		(273)
Write-offs	3,753		—		273
Ending balance	(24)		(19)		(15)

Rental Equipment, Property and Equipment (Tables)

12 Months Ended

Dec. 31, 2019

Property, Plant and Equipment [Abstract]

Summary of Rental Equipment, Property and Equipment

Our rental equipment and associated accumulated depreciation as of December 31, 2019 and 2018, respectively, consisted of the following (in thousands):


	2019		2018
Compressor units	$	370,961	$	329,697
Work-in-progress	9,129		11,868
Rental equipment	380,090		341,565
Accumulated depreciation	(162,348)		(165,459)
Rental equipment, net of accumulated depreciation	$	217,742	$	176,106

Property and equipment consists of the following at December 31, 2019 and 2018 (in thousands):


	Useful Lives (Years)	2019		2018
Land	—	$	1,290	$	1,290
Building	39	18,632		6,116
Building and leasehold improvements	39	1,168		808
Office equipment and furniture	5	2,001		1,492
Software	5	573		573
Machinery and equipment	7	3,492		3,324
Vehicles	3	7,560		6,292
Construction in Progress	—	—		8,319
Total		34,716		28,214
Less accumulated depreciation		(12,847)		(11,570)
Total		$	21,869	$	16,644

The following table depicts annual depreciation expense associated with each product line as well as our corporate activities at December 31, 2019, 2018 and 2017 (in thousands):


	2019		2018		2017
Rentals	$	22,596	$	21,611	$	20,873
Sales	275		271		267
Service & Maintenance	37		22		22
Corporate	235		50		29
Total	$	23,143	$	21,954	$	21,191

Leases (Tables)

12 Months Ended

Dec. 31, 2019

Leases [Abstract]

Schedule of Balance Sheet Impact

The impact of the new lease standard on the December 31, 2019 consolidated balance sheet was as follows:


	Classification on Consolidated Balance Sheet	December 31, 2019
		($ in thousands)
Operating lease assets	Right of use assets-operating leases	$	604

Current lease liabilities	Current operating leases	$	189
Noncurrent lease liabilities	Long-term operating leases	415
Total lease liabilities		$	604

Weighted average remaining lease term in years		2.6
Implicit Rate		3.1		%

Schedule of Cash Flow Impact

Operating lease costs are recognized on a straight-line basis over the lease term. Total operating lease costs for the year ended December 31, 2019 was approximately $548,000.


	December 31, 2019
	(in thousands)
Cash paid for amounts included in the measurement of lease liabilities
Operating lease cost ^{(1) (2)}	$	548

(1) Lease costs are classified on the Consolidated Statements of Operations in cost of sales, cost of compressors and selling, general and administrative expenses.

(2) Includes costs of $350,000 for leases with terms of 12 months or less and $198,000 for leases with terms greater than 12 months.

Schedule of Future Maturities of Lease Liabilities

The following table shows the future maturities of lease liabilities:


Years Ending December 31,	Lease Liabilities
	(in thousands)
2020	$	208
2021	172
2022	46
2023	38
2024	38
Thereafter	168
Total lease payments	670
Less: Imputed interest	(66)
Total	$	604

Schedule of Future Minimum Obligations Under Lease Commitments

Under the previous lease standard (Topic 840), future minimum obligations under lease commitments in effect at December 31, 2018 were as follows:


	Operating Leases
	(in thousands)
2019	$	298
2020	118
2021	97
2022	44
2023	35
Thereafter	15
Total	$	607

Goodwill (Tables)

12 Months Ended

Dec. 31, 2019

Goodwill and Intangible Assets Disclosure [Abstract]

Summary of Changes in Goodwill


	Goodwill, net
December 31, 2018	$	10,039
Impairments	(10,039)
December 31, 2019	$	—

Intangibles (Tables)

12 Months Ended

Dec. 31, 2019

Goodwill and Intangible Assets Disclosure [Abstract]

Schedule of Identified Finite-Lived Intangible Assets, Finite Lived

The following table represents the identified intangible assets by major asset class (in thousands):


		December 31, 2019										December 31, 2018

	Useful Life (years)	Gross Carrying Value		Accumulated Amortization		Net Book Value		Gross Carrying Value		Accumulated Amortization		Net Book Value



Developed Technology	20	$	2,505	$	1,883	$	622	$	2,505	$	1,758	$	747
Trade Name	Indefinite	654		—		654		654		—		654
Total		$	3,159	$	1,883	$	1,276	$	3,159	$	1,758	$	1,401

Schedule of Identified Indefinite-Lived Intangible Assets

The following table represents the identified intangible assets by major asset class (in thousands):


		December 31, 2019										December 31, 2018

	Useful Life (years)	Gross Carrying Value		Accumulated Amortization		Net Book Value		Gross Carrying Value		Accumulated Amortization		Net Book Value



Developed Technology	20	$	2,505	$	1,883	$	622	$	2,505	$	1,758	$	747
Trade Name	Indefinite	654		—		654		654		—		654
Total		$	3,159	$	1,883	$	1,276	$	3,159	$	1,758	$	1,401

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2019

Income Tax Disclosure [Abstract]

Provision for Income Taxes

The (provision for) benefit from income taxes for the years ended December 31, 2019, 2018 and 2017, consists of the following (in thousands):


	2019		2018		2017
Current benefit (provision):
Federal benefit (expense)	$	86	$	164	$	(3,031)
State (expense) benefit	(55)		78		(257)
Total current benefit (provision)	31		242		(3,288)
Deferred benefit (provision):
Federal benefit (expense)	662		(314)		21,575

Total deferred benefit (expense)	662		(314)		21,575
Total benefit (provision)	$	693	$	(72)	$	18,287

Deferred Tax Assets and Liabilities

The income tax effects of temporary differences that give rise to significant portions of deferred income tax assets and (liabilities) as of December 31, 2019 and 2018, are as follows (in thousands):


	2019		2018
Deferred income tax assets:
Net operating loss carryover	$	1,519	$	2,730
Stock compensation	580		746
Deferred compensation	$	389	$	243
Other	321		197
Total deferred income tax assets	$	2,809	$	3,916

Deferred income tax liabilities:
Property and equipment	$	(33,761)	(35,030)
Goodwill and other intangible assets	(291)		(573)
Other	—		(219)
Total deferred income tax liabilities	(34,052)		(35,822)
Net deferred income tax liabilities	$	(31,243)	$	(31,906)

Effective Income Tax Rate Reconciliation

The effective tax rate for the years ended December 31, 2019, 2018 and 2017, differs from the statutory rate as follows:


	2019		2018		2017
Statutory rate	21.0	%	21.0	%	34.0	%
State and local taxes	(3.7)	%	1.5	%	1.5	%
Uncertain tax position	—	%	(139.1)	%	—	%
Goodwill impairment	(13.7)	%	—	%	—	%
Research and development credit	1.4	%	92.2	%	—	%
Stock based compensation	(0.8)	%	10.0	%	(14.3)	%
Nondeductible compensation	(0.3)	%	(7.8)	%	—	%
Domestic production credit	—	%	—	%	(15.2)	%

Other	0.9	%	3.9	%	(1.5)	%
Effective rate	4.8	%	(18.3)	%	4.5	%
Deferred re-measurement for rate change	—	%	—	%	(1218.0)	%
Effective rate	4.8	%	(18.3)	%	(1213.5)	%

Uncertain tax positions

A reconciliation of the beginning and ending amount of uncertain tax positions is as follows (in thousands):


Balance at January 1, 2019	$	578
Additions based on tax positions related to current year	—
Reductions for tax positions of prior years	(578)


Balance at December 31, 2019	$	—

Rental Activity (Tables)

12 Months Ended

Dec. 31, 2019

Leases [Abstract]

Schedule of Future Minimum Rent Payments Receivable

Future minimum rent payments for arrangements not on a month-to-month basis at December 31, 2019 are as follows:


Years Ending December 31,
(in thousands)
2020	$	25,924
2021	$	18,489
2022	$	16,310
2023	$	12,507
2024	$	9,788
Thereafter	$	2,366
Total	$	85,384

Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2019

Share-based Payment Arrangement [Abstract]

Summary of Restricted Stock Activity

A summary of all restricted stock/units activity as of December 31, 2017, 2018 and 2019 and changes during the years then ended are presented below.


	Number of Shares	Weighted Average Exercise Price		Weighted Average Remaining Contractual Life (years)	Aggregate Intrinsic Value (in thousands)
Outstanding, December 31, 2016	139,451	$	21.34	9.13	$	4,483
Granted	126,432	27.06		—	3,421
Vested	(81,494)	21.20		—	2,361
Canceled/Forfeited	—	—		—	—
Outstanding, December 31, 2017	184,389	$	25.32	8.83	$	4,831
Granted	140,988	24.55		—	3,461
Vested	(110,747)	23.97		—	2,806
Canceled/Forfeited	—	—		—	—
Outstanding, December 31, 2018	214,630	$	25.51	8.85	$	3,529
Granted	199,810	17.16		—	3,433
Vested	(134,674)	24.26		—	2,807
Canceled/Forfeited	—	—		—	—
Outstanding, December 31, 2019	279,766	$	20.15	8.77	$	3,430

Stock Options Fair Value Assumptions


Weighted average Black -Scholes fair value assumption during the year ended December 31, are as follows:	2017
Risk free rate	2.12	%
Expected life	6 years
Expected volatility	39.59	%
Expected dividend yield	—

Summary of Option Activity

A summary of all option activity as of December 31, 2017, 2018 and 2019 and changes during the years then ended are presented below:


	Number of Shares	Weighted Average Grant Date Fair Value		Weighted Average Remaining Contractual Life (years)	Aggregate Intrinsic Value (in thousands)
Outstanding, December 31, 2016	350,186	$	19.45	4.25	$	4,453
Granted	32,750	28.15		—	—
Exercised	(55,666)	20.12		—	446

Outstanding, December 31, 2017	327,270	$	20.21	4.28	$	2,255

Granted	—	—		—	—
Exercised	(38,250)	17.19		—	216
Canceled/Forfeited	(5,534)	24.02		—	—
Outstanding, December 31, 2018	283,686	$	20.46	3.58	$	434
Granted	—	—		—	—
Exercised	(56,352)	8.97		—	474
Canceled/Forfeited	(8,000)	21.60		—	—
Expired	(11,000)	17.74		—	—
Outstanding, December 31, 2019	208,334	$	23.67	3.66	$	—
Exercisable, December 31, 2019	197,901	$	23.43	3.48	$	—

Summary of Stock Options Outstanding

The following table summarizes information about our stock options outstanding at December 31, 2019:


Range of Exercise Prices	Options Outstanding												Options Exercisable
		Shares		Weighted Average Remaining Contractual Life (years)			Weighted Average Exercise Price		Shares			Weighted Average Exercise Price

$0.01-15.70	8,500		2.07		$	14.89		8,500		$	14.89
$15.71-17.81	26,000		0.74		17.40			26,000		17.40
$17.82-20.48	50,500		1.34		19.43			50,500		19.43
$20.49-33.36	123,334		5.34		27.33			112,901		27.26
	208,334		3.66		$	23.67		197,901		$	23.43

Summary of the Status of Unvested Stock Options

The summary of the status of our unvested stock options as of December 31, 2019 and changes during the year then ended is presented below.


Unvested stock options:	Shares	Weighted Average Grant Date Fair Value
Unvested at December 31, 2018	20,865	$	11.93
Granted	—	—
Vested	(10,432)	11.93
Canceled/Forfeited	—	—
Unvested at December 31, 2019	10,433	$	11.93

(Loss) Earnings per Share (Tables)

12 Months Ended

Dec. 31, 2019

Earnings Per Share [Abstract]

Computation of Basic and Diluted Earnings Per Share

The following table sets forth the computation of basic and diluted (loss) earnings per share (in thousands, except per share amounts):


	Year Ended December 31,
	2019		2018		2017
Numerator:
Net (loss) income	$	(13,864)	$	(466)	$	19,794
Denominator for basic net (loss) income per common share:
Weighted average common shares outstanding	13,114		12,965		12,831
Denominator for diluted net (loss) income per share:
Weighted average common shares outstanding	13,114		12,965		12,831
Dilutive effect of stock options and restricted shares	—		—		279
Diluted weighted average shares	13,114		12,965		13,110
(Loss) earnings per common share:
Basic	$	(1.06)	$	(0.04)	$	1.54
Diluted	$	(1.06)	$	(0.04)	$	1.51

Quarterly Financial Data - Unaudited (Tables)

12 Months Ended

Dec. 31, 2019

Quarterly Financial Data [Abstract]

Quarterly Financial Data

(in thousands, except per share)


2019	Q1		Q2		Q3		Q4		Total
Total revenue	$	17,991	$	19,895	$	20,852	$	19,706	$	78,444
Operating income (loss)	(145)		302		(14,021)		(1,289)		(15,153)
Net income (loss)	98		327		(12,579)		(1,710)		(13,864)
Earnings (loss) per share, basic	0.01		0.02		(0.96)		(0.13)		(1.06)
Earnings (loss) per share, diluted	0.01		0.02		(0.96)		(0.13)		(1.06)
Earnings (loss) per share, year to date, basic	0.01		0.03		(0.93)		(1.06)		(1.06)
Earnings (loss) per share, year to date, diluted	0.01		0.03		(0.93)		(1.06)		(1.06)


2018	Q1		Q2		Q3		Q4		Total
Total revenue	$	14,718	$	18,204	$	16,396	$	16,160	$	65,478
Operating income (loss)	305		179		(500)		(491)		(507)
Net income (loss)	190		211		(118)		(749)		(466)
Earnings (loss) per share, basic	0.01		0.02		(0.01)		(0.06)		(0.04)
Earnings (loss) per share, diluted	0.01		0.02		(0.01)		(0.06)		(0.04)

Revisions to our unaudited quarterly financial data are as follows:


	For the Three Months Ended September 30, 2019
($ in thousands, except per share)	As Reported		Revisions		As Revised
Total revenue	$	20,852	$	—	$	20,852
Operating loss	(13,561)		(460)		(14,021)
Net loss	(12,232)		(347)		(12,579)
Loss per share, basic	(0.93)		(0.03)		(0.96)
Loss per share, diluted	(0.93)		(0.03)		(0.96)


	For the Three Months Ended June 30, 2019
($ in thousands, except per share)	As Reported		Revisions		As Revised
Total revenue	$	19,895	$	—	$	19,895
Operating income (loss)	593		(291)		302
Net income (loss)	573		(246)		327
Earnings (loss) per share, basic	0.04		(0.02)		0.02
Earnings (loss) per share, diluted	0.04		(0.02)		0.02


	For the Three Months Ended March 31, 2019
($ in thousands, except per share)	As Reported		Revisions		As Revised
Total revenue	$	17,991	$	—	$	17,991
Operating income (loss)	209		(354)		(145)
Net income (loss)	357		(259)		98
Earnings (loss) per share, basic	0.03		(0.02)		0.01
Earnings (loss) per share, diluted	0.03		(0.02)		0.01


	For the Three Months Ended December 31, 2018
($ in thousands, except per share)	As Reported		Revisions		As Revised
Total revenue	$	16,160	$	—	$	16,160
Operating loss	106		(597)		(491)
Net loss	(282)		(467)		(749)
Loss per share, basic	(0.02)		(0.04)		(0.06)
Loss per share, diluted	(0.02)		(0.04)		(0.06)


	For the Three Months Ended September 30, 2018
($ in thousands, except per share)	As Reported		Revisions		As Revised
Total revenue	$	16,396	$	—	$	16,396
Operating (loss)	(44)		(456)		(500)
Net income (loss)	236		(354)		(118)
Earnings (loss) per share, basic	0.02		(0.03)		(0.01)
Earnings (loss) per share, diluted	0.02		(0.03)		(0.01)


	For the Three Months Ended June 30, 2018
($ in thousands, except per share)	As Reported		Revisions		As Revised
Total revenue	$	18,204	$	—	$	18,204
Operating income (loss)	226		(47)		179
Net income (loss)	247		(36)		211
Earnings (loss) per share, basic	0.02		—		0.02
Earnings (loss) per share, diluted	0.02		—		0.02


	For the Three Months Ended March 31, 2018
($ in thousands, except per share)	As Reported		Revisions		As Revised
Total revenue	$	14,718	$	—	$	14,718
Operating income (loss)	350		(45)		305
Net income (loss)	225		(35)		190
Earnings (loss) per share, basic	0.02		(0.01)		0.01
Earnings (loss) per share, diluted	0.02		(0.01)		0.01

Revisions of Prior Period Financial Statements (Tables)

12 Months Ended

Dec. 31, 2019

Accounting Changes and Error Corrections [Abstract]

Schedule of Revisions of Prior Period Financial Statements

These revisions are summarized in the tables below.

Revised Consolidated Balance Sheet


	As of December 31, 2018
($ in thousands)	As Reported		Revisions		As Revised
Assets
Inventory	$	30,974	$	(784)	$	30,190
Prepaid income taxes	3,148		40		3,188
Prepaid expenses and other	2,430		(734)		1,696
Total current assets	96,399		(1,478)		94,921
Rental equipment, net of accumulated depreciation	175,886		220		176,106
Property and equipment, net of accumulated depreciation	16,587		57		16,644
Total assets	305,401		(1,201)		304,200

Liabilities and Stockholders' Equity
Deferred income tax liability	$	32,158	$	(252)	$	31,906
Total liabilities	45,220		(252)		44,968
Retained earnings	152,291		(949)		151,342
Total stockholders' equity	260,181		(949)		259,232
Total liabilities and stockholders' equity	305,401		(1,201)		304,200

Revised Consolidated Statements of Income


	For the Year Ended December 31, 2018
($ in thousands, except per share)	As Reported		Revisions		As Revised
Total revenue	$	65,478	$	—	$	65,478
Operating costs and expenses:
Cost of rentals, exclusive of depreciation stated separately below	20,746		1,114		21,860
Depreciation and amortization	22,049		31		22,080
Total operating costs and expenses	64,840		1,145		65,985
Operating income (loss)	638		(1,145)		(507)
Income (loss) before provision for income taxes	751		(1,145)		(394)
Provision for income taxes:
Current benefit (expense)	248		(6)		242
Deferred (expense) benefit	(573)		259		(314)
Income tax (expense) benefit	(325)		253		(72)
Net income (loss)	426		(892)		(466)
Earnings (loss) per share, basic	0.03		(0.07)		(0.04)
Earnings (loss) per share, diluted	0.03		(0.07)		(0.04)


	For the Year Ended December 31, 2017
($ in thousands, except per share)	As Reported		Revisions		As Revised
Total revenue	$	67,693	$	—	$	67,693
Operating costs and expenses:
Cost of rentals, exclusive of depreciation stated separately below	18,078		82		18,160
Depreciation and amortization	21,302		14		21,316
Total operating costs and expenses	66,126		96		66,222
Operating income (loss)	1,567		(96)		1,471
Income (loss) before provision for income taxes	1,603		(96)		1,507
Provision for income taxes:
Current (expense) benefit	(3,334)		46		(3,288)
Deferred benefit (expense)	21,582		(7)		21,575
Income tax benefit	18,248		39		18,287
Net income (loss)	19,851		(57)		19,794
Earnings (loss) per share, basic	1.55		(0.01)		1.54
Earnings (loss) per share, diluted	1.51		—		1.51

Revised Consolidated Statements of Stockholders' Equity


	For the Year Ended December 31, 2018
($ in thousands)	As Reported		Revisions		As Revised
Net income (loss)	$	426	$	(892)	$	(466)
Retained earnings	152,291		(949)		151,342
Total stockholders' equity	260,181		(949)		259,232


	For the Year Ended December 31, 2017
($ in thousands)	As Reported		Revisions		As Revised
Net income (loss)	$	19,851	$	(57)	$	19,794
Retained earnings	151,865		(57)		151,808
Total stockholders' equity	257,319		(57)		257,262

Revised Consolidated Statements of Cash Flows


	For the Year Ended December 31, 2018
($ in thousands)	As Reported		Revisions		As Revised
Cash flows from operating activities:
Net income (loss)	$	426	$	(892)	$	(466)
Depreciation and amortization	22,049		31		22,080
Deferred taxes	573		(259)		314
Inventory (increase) decrease	(5,757)		655		(5,102)
Prepaid income taxes and prepaid expenses (increase) decrease	(1,318)		740		(578)
Net cash provided by operating activities	23,414		275		23,689
Cash flows from investing activities:
Purchase of rental equipment, property and other equipment	(39,790)		(275)		(40,065)
Net cash used in investing activities	(40,010)		(275)		(40,285)
Net change in cash and cash equivalents	(16,580)		—		(16,580)


	For the Year Ended December 31, 2017
($ in thousands)	As Reported		Revisions		As Revised
Cash flows from operating activities:
Net income (loss)	$	19,851	$	(57)	$	19,794
Depreciation and amortization	21,302		14		21,316
Deferred taxes	(21,582)		7		(21,575)
Inventory (increase) decrease	(5,350)		129		(5,221)
Prepaid income taxes and prepaid expenses increase	(1,806)		(46)		(1,852)
Net cash provided by operating activities	17,452		47		17,499
Cash flows from investing activities:
Purchase of rental equipment, property and other equipment	(13,489)		(47)		(13,536)
Net cash used in investing activities	(12,791)		(47)		(12,838)
Net change in cash and cash equivalents	5,114		—		5,114

Summary of Significant Accounting Policies (Narrative) (Details)	3 Months Ended								9 Months Ended	12 Months Ended
	Dec. 31, 2019 USD ($)	Sep. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Sep. 30, 2019 USD ($)	Dec. 31, 2019 USD ($) segment	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Jan. 01, 2019 USD ($)
Revenue from External Customer [Line Items]
Cash equivalents, qualification, maximum original maturity of short-term investments										3 months
Customer deposit requirements, large custom contracts, maximum percentage										50.00%
Allowance for doubtful accounts	$ 918,000				$ 291,000					$ 918,000	$ 291,000
Revenues	19,706,000	$ 20,852,000	$ 19,895,000	$ 17,991,000	16,160,000	$ 16,396,000	$ 18,204,000	$ 14,718,000		78,444,000	65,478,000	$ 67,693,000
Revenue recognized										48,000	176,000
Impairments		10,000,000.0								10,039,000	0	0
Product warranty reserves	74,000				22,000					74,000	22,000
Uncertain tax positions	0									$ 0
Number of business segments \| segment										1
Right of use assets	604,000				0					$ 604,000	0		$ 451,000
Operating lease, liability	$ 604,000				0					604,000	0		451,000
Operating costs and expenses										$ 93,597,000	65,985,000	66,222,000
Minimum
Revenue from External Customer [Line Items]
Rental arrangements, original term										6 months
Maximum
Revenue from External Customer [Line Items]
Rental arrangements, original term										60 months
Revisions \| Revision Of Prior Period Financial Statements
Revenue from External Customer [Line Items]
Revenues		$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0			0	0
Operating costs and expenses									$ 1,100,000		1,145,000	$ 96,000
Developed Technology
Revenue from External Customer [Line Items]
Intangible assets, useful life										20 years
Intangible assets, weighted average remaining life										5 years
Bill and Hold Arrangement
Revenue from External Customer [Line Items]
Revenues										$ 11,600,000	$ 8,300,000
Accounting Standards Update 2016-02
Revenue from External Customer [Line Items]
Right of use assets													451,000
Operating lease, liability													$ 451,000
Accounts Receivable \| Customer Concentration Risk
Revenue from External Customer [Line Items]
Concentration risk, percentage										35.00%	26.00%

Summary of Significant Accounting Policies (Schedule of Allowance for Doubtful Accounts) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	$ (291)	$ (569)	$ (597)
Accruals	(664)	0	(90)
Recoveries	0	185	0
Write-offs	37	93	118
Ending balance	$ (918)	$ (291)	$ (569)

Summary of Significant Accounting Policies (Disaggregation of Revenue) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers									$ 21,743	$ 17,712	$ 21,647
Add: ASC 842 rental revenue									56,701	47,766	46,046
Total revenue	$ 19,706	$ 20,852	$ 19,895	$ 17,991	$ 16,160	$ 16,396	$ 18,204	$ 14,718	78,444	65,478	67,693
Compressors - sales
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers									15,185	10,994	13,382
Flares - sales
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers									959	2,535	2,755
Other (Parts/Rebuilds) - sales
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers									3,619	2,740	4,071
Service and maintenance
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers									$ 1,980	$ 1,443	$ 1,439

Summary of Significant Accounting Policies (Contract Balances) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Accounting Policies [Abstract]
Accounts receivable - contracts with customers	$ 3,061	$ 2,390
Accounts receivable - ASC 842	6,963	5,120
Total Accounts Receivable	10,024	7,510
Less: Allowance for doubtful accounts	(918)	(291)
Total Accounts Receivable, net	9,106	7,219
Deferred income	$ 640	$ 81

Summary of Significant Accounting Policies (Cumulative Effect of Changes from Adoption of ASU) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Jan. 01, 2019	Dec. 31, 2018
ASSETS
Right of use assets	$ 604	$ 451	$ 0
Liabilities [Abstract]
Current operating leases	189	126	0
Long-term operating leases	415	325	0
Total lease liabilities	$ 604	451	$ 0
Accounting Standards Update 2016-02
ASSETS
Right of use assets		451
Liabilities [Abstract]
Current operating leases		126
Long-term operating leases		325
Total lease liabilities		$ 451

Summary of Significant Accounting Policies (Concentration Risk) (Details) - Customer Concentration Risk	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Accounts Receivable
Concentration Risk [Line Items]
Concentration risk, percentage	35.00%	26.00%
Oxy \| Sales and Rental Income
Concentration Risk [Line Items]
Concentration risk, percentage	36.00%	28.00%	15.00%
Oxy \| Accounts Receivable
Concentration Risk [Line Items]
Concentration risk, percentage	35.00%	26.00%
Devon \| Sales and Rental Income
Concentration Risk [Line Items]
Concentration risk, percentage			20.00%

Summary of Significant Accounting Policies (Property and Equipment) (Details)	12 Months Ended
	Dec. 31, 2019
Minimum
Property, Plant and Equipment [Line Items]
Property and equipment, estimated useful life	3 years
Maximum
Property, Plant and Equipment [Line Items]
Property and equipment, estimated useful life	39 years
Rental Equipment \| Minimum
Property, Plant and Equipment [Line Items]
Property and equipment, estimated useful life	15 years
Rental Equipment \| Maximum
Property, Plant and Equipment [Line Items]
Property and equipment, estimated useful life	25 years

Inventory (Narrative) (Details) $ in Thousands	3 Months Ended		12 Months Ended
Inventory (Narrative) (Details) $ in Thousands	Dec. 31, 2019 USD ($)	Sep. 30, 2019 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($) compressor	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Inventory Disclosure [Abstract]
Allowance for inventory obsolescence	$ 24		$ 24	$ 19	$ 15	$ 15
Available-for-sale or rental, compressor units \| compressor				7
Available-for-sale or rental, finished goods				$ 1,000
Inventory allowance	$ 408	$ 3,400	$ 3,758	$ 0	$ 273

Inventory (Schedule of Inventory) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Inventory Disclosure [Abstract]
Raw materials - current	$ 19,388	$ 26,152
Work-in-process	1,692	3,016
Finished goods	0	1,022
Inventory - current	21,080	30,190
Raw materials - long term (net of allowances of $24 and $19, respectively	1,068	3,980
Inventory	22,148	34,170
Allowance for inventory obsolescence	$ 24	$ 19	$ 15	$ 15

Inventory (Schedule of Inventory Allowance) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Inventory Valuation Reserves [Roll Forward]
Beginning balance	$ (19)	$ (15)	$ (15)
Accruals	(3,758)	(4)	(273)
Write-offs	3,753	0	273
Ending balance	$ (24)	$ (19)	$ (15)

Rental Equipment, Property and Equipment (Schedule of Rental Equipment, Property and Equipment) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 34,716	$ 28,214
Less accumulated depreciation	(12,847)	(11,570)
Property and equipment, net	21,869	16,644
Depreciation	23,143	21,954	$ 21,191
Land
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 1,290	1,290
Building
Property, Plant and Equipment [Line Items]
Useful Lives	39 years
Property and equipment, gross	$ 18,632	6,116
Building and leasehold improvements
Property, Plant and Equipment [Line Items]
Useful Lives	39 years
Property and equipment, gross	$ 1,168	808
Office equipment and furniture
Property, Plant and Equipment [Line Items]
Useful Lives	5 years
Property and equipment, gross	$ 2,001	1,492
Software
Property, Plant and Equipment [Line Items]
Useful Lives	5 years
Property and equipment, gross	$ 573	573
Machinery and equipment
Property, Plant and Equipment [Line Items]
Useful Lives	7 years
Property and equipment, gross	$ 3,492	3,324
Vehicles
Property, Plant and Equipment [Line Items]
Useful Lives	3 years
Property and equipment, gross	$ 7,560	6,292
Construction in Progress
Property, Plant and Equipment [Line Items]
Property and equipment, gross	0	8,319
Property, Plant, and Equipment, Excluding Rental Equipment
Property, Plant and Equipment [Line Items]
Depreciation	1,700	1,100	1,200
Rental Equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	380,090	341,565
Less accumulated depreciation	(162,348)	(165,459)
Property and equipment, net	217,742	176,106
Depreciation	21,400	20,900	$ 20,000
Rental Equipment \| Compressor units
Property, Plant and Equipment [Line Items]
Property and equipment, gross	370,961	329,697
Rental Equipment \| Work-in-progress
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 9,129	$ 11,868
Minimum
Property, Plant and Equipment [Line Items]
Useful Lives	3 years
Minimum \| Rental Equipment
Property, Plant and Equipment [Line Items]
Useful Lives	15 years
Maximum
Property, Plant and Equipment [Line Items]
Useful Lives	39 years
Maximum \| Rental Equipment
Property, Plant and Equipment [Line Items]
Useful Lives	25 years

Rental Equipment, Property and Equipment (Narrative) (Details) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019 USD ($)	Sep. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2019 USD ($) compressor $ / shares	Dec. 31, 2018 USD ($) compressor	Dec. 31, 2017 USD ($)
Property, Plant and Equipment [Line Items]
Depreciation									$ 23,143	$ 21,954	$ 21,191
Net income (loss)	$ (1,710)	$ (12,579)	$ 327	$ 98	$ (749)	$ (118)	$ 211	$ 190	(13,864)	(466)	19,794
Retirement of rental equipment									1,512	0	0
Property, Plant, and Equipment, Excluding Rental Equipment
Property, Plant and Equipment [Line Items]
Depreciation									$ 1,700	$ 1,100	1,200
Rental Compressor Unit
Property, Plant and Equipment [Line Items]
Number of units retired \| compressor									327	13
Rental Compressor Unit \| Loss On Retirement of Rental Equipment
Property, Plant and Equipment [Line Items]
Retirement of rental equipment									$ 1,500
Revisions \| Revision Of Prior Period Financial Statements
Property, Plant and Equipment [Line Items]
Depreciation									1,470
Net income (loss)		$ (347)	$ (246)	$ (259)	$ (467)	$ (354)	$ (36)	$ (35)	$ 1,130	$ (892)	(57)
Earnings per share, basic and diluted (in dollars per share) \| $ / shares									$ 0.09
Rental Equipment
Property, Plant and Equipment [Line Items]
Depreciation									$ 21,400	$ 20,900	$ 20,000
Rental Equipment \| Compressor Units, 1,380 Horsepower
Property, Plant and Equipment [Line Items]
Useful Lives									25 years
Minimum
Property, Plant and Equipment [Line Items]
Useful Lives									3 years
Minimum \| Rental Equipment
Property, Plant and Equipment [Line Items]
Useful Lives									15 years
Minimum \| Rental Equipment \| Compressor Units, 400-600 Horsepower
Property, Plant and Equipment [Line Items]
Useful Lives									15 years
Minimum \| Rental Equipment \| Compressor Unit, Peer Horsepower
Property, Plant and Equipment [Line Items]
Useful Lives									20 years
Maximum
Property, Plant and Equipment [Line Items]
Useful Lives									39 years
Maximum \| Rental Equipment
Property, Plant and Equipment [Line Items]
Useful Lives									25 years
Maximum \| Rental Equipment \| Compressor Units, 400-600 Horsepower
Property, Plant and Equipment [Line Items]
Useful Lives									20 years
Maximum \| Rental Equipment \| Compressor Unit, Peer Horsepower
Property, Plant and Equipment [Line Items]
Useful Lives									30 years

Rental Equipment, Property and Equipment (Depreciation Expense by Product Line) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Depreciation	$ 23,143	$ 21,954	$ 21,191
Operating Segments
Property, Plant and Equipment [Line Items]
Depreciation	275
Corporate
Property, Plant and Equipment [Line Items]
Depreciation	235	50	29
Rentals \| Operating Segments
Property, Plant and Equipment [Line Items]
Depreciation	22,596	21,611	20,873
Sales \| Operating Segments
Property, Plant and Equipment [Line Items]
Depreciation		271	267
Service & Maintenance \| Operating Segments
Property, Plant and Equipment [Line Items]
Depreciation	$ 37	$ 22	$ 22

Leases (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
Leases (Narrative) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Jan. 01, 2019
Lessee, Lease, Description [Line Items]
Right of use assets	$ 604	$ 0		$ 451
Operating lease, liability	604	0		451
Lease costs	548
Short-term lease cost	350
Operating lease, cost	$ 198
Operating leases, rent expense		$ 433	$ 310
Accounting Standards Update 2016-02
Lessee, Lease, Description [Line Items]
Right of use assets				451
Operating lease, liability				$ 451
Minimum
Lessee, Lease, Description [Line Items]
Remaining lease term	1 year
Maximum
Lessee, Lease, Description [Line Items]
Remaining lease term	10 years

Leases (Balance Sheet Impact) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Jan. 01, 2019	Dec. 31, 2018
Leases [Abstract]
Right of use assets	$ 604	$ 451	$ 0
Current operating leases	189	126	0
Long-term operating leases	415	325	0
Total lease liabilities	$ 604	$ 451	$ 0
Weighted average remaining lease term in years	2 years 7 months 6 days
Implicit Rate	3.10%

Leases (Cash Flow Impact) (Details) $ in Thousands	12 Months Ended
Leases (Cash Flow Impact) (Details) $ in Thousands	Dec. 31, 2019 USD ($)
Leases [Abstract]
Operating lease cost	$ 548

Leases (Future Maturities of Lease Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Jan. 01, 2019	Dec. 31, 2018
Leases [Abstract]
2020	$ 208
2021	172
2022	46
2023	38
2024	38
Thereafter	168
Total lease payments	670
Less: Imputed interest	(66)
Total	$ 604	$ 451	$ 0

Leases (Future Minimum Obligations Under Lease Commitments) (Details) $ in Thousands	Dec. 31, 2018 USD ($)
Leases [Abstract]
2019	$ 298
2020	118
2021	97
2022	44
2023	35
Thereafter	15
Total	$ 607

Goodwill (Narrative) (Details) - USD ($)	3 Months Ended	12 Months Ended
Goodwill (Narrative) (Details) - USD ($)	Sep. 30, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Impairments	$ 10,000,000.0	$ 10,039,000	$ 0	$ 0

Goodwill (Summary of Changes in Goodwill) (Details) - USD ($)	3 Months Ended	12 Months Ended
	Sep. 30, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Goodwill [Roll Forward]
Goodwill, beginning balance		$ 10,039,000
Impairments	$ (10,000,000.0)	(10,039,000)	$ 0	$ 0
Goodwill, ending balance		$ 0	$ 10,039,000

Intangibles (Details) - USD ($)	12 Months Ended
Intangibles (Details) - USD ($)	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Intangible Assets [Line Items]
Intangibles, net of accumulated amortization	$ 1,276,000	$ 1,401,000
Amortization expense	125,000	125,000	$ 125,000
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract]
2020	125,000
2021	125,000
2022	125,000
2023	125,000
2024	125,000
Finite-Lived Intangible Assets, Net [Abstract]
Gross Carrying Value	3,159,000	3,159,000
Accumulated Amortization	1,883,000	1,758,000
Net Book Value	1,276,000	1,401,000
Impairment of intangible assets	0	0
Trade Name
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract]
Indefinite-lived intangible asset, gross carrying value	654,000
Finite-Lived Intangible Assets, Net [Abstract]
Gross Carrying Value	654,000	654,000
Accumulated Amortization	0	0
Net Book Value	$ 654,000	654,000
Developed Technology
Finite-Lived Intangible Assets, Net [Abstract]
Intangible assets, useful life	20 years
Gross Carrying Value	$ 2,505,000	2,505,000
Accumulated Amortization	1,883,000	1,758,000
Net Book Value	$ 622,000	$ 747,000

Credit Facility (Details)	12 Months Ended
Credit Facility (Details)	Dec. 31, 2019 USD ($) loan	Dec. 31, 2018 USD ($)
Line of Credit Facility [Line Items]
Line of credit	$ 417,000	$ 0
Weighted average interest rate	3.06%
Revolving Credit Facility
Line of Credit Facility [Line Items]
Maximum borrowing capacity	$ 30,000,000
Potential increase in borrowing capacity	20,000,000
Potential maximum borrowing capacity	$ 50,000,000
Borrowing base, component, % of eligible accounts receivable	80.00%
Borrowing base, component, % of eligible inventory	50.00%
Borrowing base, allowable share of total commitment amount attributable to inventory component	50.00%
Borrowing base, component, % of eligible equipment inventory	75.00%
Borrowing base amount available	$ 29,500,000
Line of credit	$ 417,000
Revolving Credit Facility \| LIBOR-based Rate
Line of Credit Facility [Line Items]
Variable rate, applicable margin	1.50%
Revolving Credit Facility \| CB Floating Rate
Line of Credit Facility [Line Items]
Variable rate, applicable margin	1.25%
Revolving Credit Facility \| Maximum
Line of Credit Facility [Line Items]
Maximum leverage ratio allowed	2.50
Default trigger, certain defaults of other company indebtedness, amount	$ 50,000
Default trigger, rendering of certain judgments, amount	$ 150,000
Revolving Credit Facility \| Maximum \| LIBOR-based Rate
Line of Credit Facility [Line Items]
Reference rate, number of allowable LIBOR-based borrowings outstanding (in loans) \| loan	3
Revolving Credit Facility \| Minimum
Line of Credit Facility [Line Items]
Minimum commitment coverage ratio allowed	2.00

Income Taxes (Components of Provision for Income Taxes) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Current benefit (provision):
Federal benefit (expense)	$ 86	$ 164	$ (3,031)
State (expense) benefit	(55)	78	(257)
Total current benefit (provision)	31	242	(3,288)
Deferred benefit (provision):
Federal benefit (expense)	662	(314)	21,575
Total deferred benefit (expense)	662	(314)	21,575
Total income tax benefit (expense)	$ 693	$ (72)	$ 18,287

Income Taxes Income Taxes (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Tax Cuts and Jobs Act, change in tax rate, income tax expense (benefit)		$ (18,400)
Net operating loss carryforward		6,700
Income Tax Contingency [Line Items]
Tax Cuts and Jobs Act, change in tax rate, income tax expense (benefit)		(18,400)
Unrecognized Tax Benefits, Increase Resulting from Prior Period Tax Positions	$ 547
Income tax penalties and interest accrued	$ 55
Net operating loss carryforward		6,700
Tax Year 2017
Income Tax Contingency [Line Items]
Unrecognized Tax Benefits, Increase Resulting from Prior Period Tax Positions		168
Tax Year 2016
Income Tax Contingency [Line Items]
Unrecognized Tax Benefits, Increase Resulting from Prior Period Tax Positions		149
Tax Year 2015
Income Tax Contingency [Line Items]
Unrecognized Tax Benefits, Increase Resulting from Prior Period Tax Positions		$ 230

Income Taxes (Components of Deferred Tax Assets and Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Deferred income tax assets:
Net operating loss carryover	$ 1,519	$ 2,730
Stock compensation	580	746
Deferred compensation	389	243
Other	321	197
Total deferred income tax assets	2,809	3,916
Deferred income tax liabilities:
Property and equipment	(33,761)	(35,030)
Goodwill and other intangible assets	(291)	(573)
Other	0	(219)
Total deferred income tax liabilities	(34,052)	(35,822)
Net deferred income tax liabilities	$ (31,243)	$ (31,906)

Income Taxes (Income Tax Reconciliation) (Details)	12 Months Ended
Income Taxes (Income Tax Reconciliation) (Details)	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Statutory rate	21.00%	21.00%	34.00%
State and local taxes	(3.70%)	1.50%	1.50%
Uncertain tax position	0.00%	(139.10%)	0.00%
Goodwill impairment	(13.70%)	0.00%	0.00%
Research and development credit	1.40%	92.20%	0.00%
Stock based compensation	(0.80%)	10.00%	(14.30%)
Nondeductible compensation	(0.30%)	(7.80%)
Domestic production credit	0.00%	0.00%	(15.20%)
Other	0.90%	3.90%	(1.50%)
Effective rate	4.80%	(18.30%)	4.50%
Deferred re-measurement for rate change	0	0	(12.180)
Effective rate	4.80%	(18.30%)	(1213.50%)

Income Taxes (Uncertain Tax Positions) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($)
Uncertain tax positions [Roll Forward]
Balance at January 1, 2019	$ 578
Additions based on tax positions related to current year	0
Unrecognized Tax Benefits, Decrease Resulting from Prior Period Tax Positions	(578)
Balance at December 31, 2019	$ 0

Deferred Compensation Plans (Details) - USD ($)	12 Months Ended
Deferred Compensation Plans (Details) - USD ($)	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Compensation Related Costs [Abstract]
Participant's maximum compensation deferral percentage	90.00%
Company owned life insurance	$ 1,500,000	$ 1,000,000.0
Gain (loss) on company owned life insurance	218,800	(153,900)	$ 67,000
Deferred compensation obligation	$ 1,700,000	$ 1,100,000
Deferred restricted stock shares (in shares)	85,565	101,895
Deferred compensation arrangement with individual, shares issued (in shares)	89,187	34,732
Deferred compensation arrangement, fair value of shares issued	$ 1,700,000	$ 871,300

Stockholders' Equity (Details) - shares	Dec. 31, 2019	Dec. 31, 2018
Stockholders' Equity Attributable to Parent [Abstract]
Preferred stock, shares authorized (in shares)	5,000,000	5,000,000
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0

Rental Activity (Details) - USD ($) $ in Thousands	12 Months Ended
Rental Activity (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Property Subject to or Available for Operating Lease [Line Items]
Depreciation	$ 23,143	$ 21,954	$ 21,191
Operating Leases, Future Minimum Payments Receivable [Abstract]
2020	25,924
2021	18,489
2022	16,310
2023	12,507
2024	9,788
Thereafter	2,366
Total	$ 85,384
Minimum
Property Subject to or Available for Operating Lease [Line Items]
Rental arrangements, original term	6 months
Maximum
Property Subject to or Available for Operating Lease [Line Items]
Rental arrangements, original term	60 months

Stock-Based Compensation (Restricted Stock Narrative) (Details) - Restricted Stock - USD ($) $ / shares in Units, $ in Thousands					12 Months Ended
	Nov. 15, 2019	Mar. 23, 2017	Feb. 14, 2017	Jun. 18, 2014	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Jun. 20, 2019	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares outstanding (in shares)					279,766	214,630	184,389		139,451
Granted (in shares)					199,810	140,988	126,432
Granted (in dollars per share)					$ 17.16	$ 24.55	$ 27.06
Share-based compensation expense					$ 2,500	$ 2,200	$ 3,700
Total unrecognized compensation expense					$ 3,300
Unrecognized compensation cost related to stock options, weighted average period for recognition					3 years 3 months
Chief Executive Officer
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)			131,674
Award vesting period			3 years
Chief Financial Officer
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)		20,000
Granted (in dollars per share)	$ 11.18
Share-based compensation expense	$ 189
Chief Financial Officer \| Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in dollars per share)	$ 17.29
Chief Financial Officer \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in dollars per share)	$ 24.55
Vice President of Technical Services
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)		20,000
Executive Officer
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period		3 years
Director
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)					23,136
Award vesting period					1 year
2009 Restricted Stock/Units Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Additional shares authorized (in shares)				500,000
Number of shares authorized (in shares)				800,000
Shares outstanding (in shares)					123,092
Award vesting period					2 years
Share-based compensation arrangement by share-based payment award, equity instruments other than options, nonvested (in shares)					328,173
Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized (in shares)								500,000

Stock-Based Compensation (Restricted Stock Activity) (Details) - Restricted Stock - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Number of Shares
Outstanding, Beginning Balance (in shares)	214,630	184,389	139,451
Granted (in shares)	199,810	140,988	126,432
Vested (in shares)	(134,674)	(110,747)	(81,494)
Canceled/Forfeited (in shares)	0	0	0
Outstanding, Ending Balance (in shares)	279,766	214,630	184,389	139,451
Weighted Average Exercise Price
Outstanding, Beginning Balance (in dollars per share)	$ 25.51	$ 25.32	$ 21.34
Granted (in dollars per share)	17.16	24.55	27.06
Vested (in dollars per share)	24.26	23.97	21.20
Canceled/Forfeited (in dollars per share)	0	0	0
Outstanding, Ending Balance (in dollars per share)	$ 20.15	$ 25.51	$ 25.32	$ 21.34
Weighted Average Remaining Contractual Life (years)
Weighted Average Remaining Contractual Life (years)	8 years 9 months 7 days	8 years 10 months 6 days	8 years 9 months 29 days	9 years 1 month 17 days
Aggregate Intrinsic Value (in thousands)
Aggregate Intrinsic Value, Outstanding	$ 3,430	$ 3,529	$ 4,831	$ 4,483
Aggregate Intrinsic Value, Granted	3,433	3,461	3,421
Aggregate Intrinsic Value, Vested	$ 2,807	$ 2,806	$ 2,361

Stock-Based Compensation (Stock Options Narrative) (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Jun. 16, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)	0	0	32,750
Weighted average grant date fair value of options granted (in dollars per share)	$ 0	$ 0	$ 11.93
Total intrinsic value of options exercised	$ 474	$ 216	$ 446
Proceeds from exercise of stock options	506	680	1,120
Unrecognized compensation cost related to stock options	16
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense	$ 124	$ 159	$ 363
Stock Options \| 1998 Stock Option Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period	3 years
Award expiration period	10 years
Stock Options \| 1998 Stock Option Plan \| Common Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized (in shares)				1,000,000.0
Number of shares available for grant (in shares)	337,503

Stock-Based Compensation (Valuation Assumptions) (Details)	12 Months Ended
	Dec. 31, 2017
Share-based Payment Arrangement [Abstract]
Risk free rate	2.12%
Expected life	6 years
Expected volatility	39.59%
Expected dividend yield	0.00%

Stock-Based Compensation (Stock Option Activity) (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Number of Shares
Outstanding, beginning of period (in shares)	283,686	327,270	350,186
Granted (in shares)	0	0	32,750
Exercised (in shares)	(56,352)	(38,250)	(55,666)
Canceled/Forfeited (in shares)	(8,000)	(5,534)
Expired (in shares)	(11,000)
Outstanding, end of period (in shares)	208,334	283,686	327,270	350,186
Exercisable (in shares)	197,901
Weighted Average Grant Date Fair Value
Outstanding, beginning of period (in dollars per share)	$ 20.46	$ 20.21	$ 19.45
Granted (in dollars per share)	0	0	28.15
Exercised (in dollars per share)	8.97	17.19	20.12
Canceled/Forfeited, weighted average exercise price (in dollars per share)	21.60	24.02
Expired (in dollars per share)	17.74
Outstanding, end of period (in dollars per share)	23.67	$ 20.46	$ 20.21	$ 19.45
Exercisable (in dollars per share)	$ 23.43
Weighted Average Remaining Contractual Life (years)
Outstanding, weighted average remaining contractual life	3 years 7 months 28 days	3 years 6 months 29 days	4 years 3 months 10 days	4 years 3 months
Exercisable, weighted average remaining contractual life	3 years 5 months 23 days
Aggregate Intrinsic Value
Outstanding, aggregate intrinsic value	$ 0	$ 434	$ 2,255	$ 4,453
Exercised, aggregate intrinsic value	474	$ 216	$ 446
Exercisable, aggregate intrinsic value	$ 0

Stock-Based Compensation (Stock Options by Exercise Price Range) (Details)	12 Months Ended
	Dec. 31, 2019 $ / shares shares
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options outstanding, shares (in shares) \| shares	208,334
Options outstanding, weighted average remaining contractual life	3 years 7 months 28 days
Options outstanding, weighted average exercise price (in dollars per share)	$ 23.67
Options exercisable, shares (in shares) \| shares	197,901
Options exercisable, weighted average exercise price (in dollars per share)	$ 23.43
$0.01-15.70
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of exercise prices, lower limit (in dollars per share)	0.01
Range of exercise prices, upper limit (in dollars per share)	$ 15.70
Options outstanding, shares (in shares) \| shares	8,500
Options outstanding, weighted average remaining contractual life	2 years 25 days
Options outstanding, weighted average exercise price (in dollars per share)	$ 14.89
Options exercisable, shares (in shares) \| shares	8,500
Options exercisable, weighted average exercise price (in dollars per share)	$ 14.89
$15.71-17.81
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of exercise prices, lower limit (in dollars per share)	15.71
Range of exercise prices, upper limit (in dollars per share)	$ 17.81
Options outstanding, shares (in shares) \| shares	26,000
Options outstanding, weighted average remaining contractual life	8 months 26 days
Options outstanding, weighted average exercise price (in dollars per share)	$ 17.40
Options exercisable, shares (in shares) \| shares	26,000
Options exercisable, weighted average exercise price (in dollars per share)	$ 17.40
$17.82-20.48
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of exercise prices, lower limit (in dollars per share)	17.82
Range of exercise prices, upper limit (in dollars per share)	$ 20.48
Options outstanding, shares (in shares) \| shares	50,500
Options outstanding, weighted average remaining contractual life	1 year 4 months 2 days
Options outstanding, weighted average exercise price (in dollars per share)	$ 19.43
Options exercisable, shares (in shares) \| shares	50,500
Options exercisable, weighted average exercise price (in dollars per share)	$ 19.43
$20.49-33.36
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of exercise prices, lower limit (in dollars per share)	20.49
Range of exercise prices, upper limit (in dollars per share)	$ 33.36
Options outstanding, shares (in shares) \| shares	123,334
Options outstanding, weighted average remaining contractual life	5 years 4 months 2 days
Options outstanding, weighted average exercise price (in dollars per share)	$ 27.33
Options exercisable, shares (in shares) \| shares	112,901
Options exercisable, weighted average exercise price (in dollars per share)	$ 27.26

Stock-Based Compensation (Summary of Unvested Stock Options) (Details) - $ / shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Shares
Unvested, beginning of period (in shares)	20,865
Granted (in shares)	0	0	32,750
Vested (in shares)	(10,432)
Canceled/Forfeited (in shares)	0
Unvested, end of period (in shares)	10,433	20,865
Weighted Average Grant Date Fair Value
Unvested, beginning of period (in dollars per share)	$ 11.93
Granted (in dollars per share)	0	$ 0	$ 11.93
Vested (in dollars per share)	11.93
Canceled/Forfeited (in dollars per share)	0
Unvested, end of period (in dollars per share)	$ 11.93	$ 11.93

(Loss) Earnings per Share (Basic and Diluted) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								6 Months Ended	9 Months Ended	12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Sep. 30, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Net Income (Loss) Attributable to Parent [Abstract]
Net (loss) income	$ (1,710)	$ (12,579)	$ 327	$ 98	$ (749)	$ (118)	$ 211	$ 190			$ (13,864)	$ (466)	$ 19,794
Denominator for basic net income per common share:
Weighted average common shares outstanding, Basic (in shares)											13,114,000	12,965,000	12,831,000
Denominator for diluted net income per share:
Dilutive effect of stock options and restricted shares (in shares)											0	0	279,000
Weighted average common shares outstanding, Diluted (in shares)											13,114,000	12,965,000	13,110,000
Earnings Per Share, Basic and Diluted [Abstract]
Earnings (loss) per share - Basic (in dollars per share)	$ (0.13)	$ (0.96)	$ 0.02	$ 0.01	$ (0.06)	$ (0.01)	$ 0.02	$ 0.01	$ 0.03	$ (0.93)	$ (1.06)	$ (0.04)	$ 1.54
Earnings (loss) per share - Diluted (in dollars per share)	$ (0.13)	$ (0.96)	$ 0.02	$ 0.01	$ (0.06)	$ (0.01)	$ 0.02	$ 0.01	$ 0.03	$ (0.93)	$ (1.06)	$ (0.04)	$ 1.51
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities (in shares)											0	0
Stock Options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities (in shares)													83,917
Range of exercise prices, lower limit (in dollars per share)													$ 28.15
Range of exercise prices, upper limit (in dollars per share)													$ 33.36

Related Party (Narrative) (Details) - Corporate Joint Venture - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2016
Related Party Transaction [Line Items]
Purchases from joint venture	$ 1.0
N-G, LLC
Related Party Transaction [Line Items]
Percent ownership		50.00%
Genis Holdings, LLC \| N-G, LLC
Related Party Transaction [Line Items]
Percent ownership		50.00%

Commitments and Contingencies (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
401(k) plan, minimum eligibility age	18 years
401(k) plan, requisite service period	2 months
401(k) plan, maximum annual contribution per employee, percent	100.00%
401(k) plan, employer's matching contribution, annual vesting percentage	20.00%
401(k) plan, employer contribution, ultimate vesting percentage	100.00%
401(k) plan, employer's matching contribution, vesting term	6 years
401(k) plan, employer contribution amount	$ 393	$ 355	$ 301

Quarterly Financial Data - Unaudited (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								6 Months Ended	9 Months Ended	12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Sep. 30, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Total revenue	$ 19,706	$ 20,852	$ 19,895	$ 17,991	$ 16,160	$ 16,396	$ 18,204	$ 14,718			$ 78,444	$ 65,478	$ 67,693
Operating income (loss)	(1,289)	(14,021)	302	(145)	(491)	(500)	179	305			(15,153)	(507)	1,471
Net income (loss)	$ (1,710)	$ (12,579)	$ 327	$ 98	$ (749)	$ (118)	$ 211	$ 190			$ (13,864)	$ (466)	$ 19,794
Earnings (loss) per share - Basic (in dollars per share)	$ (0.13)	$ (0.96)	$ 0.02	$ 0.01	$ (0.06)	$ (0.01)	$ 0.02	$ 0.01	$ 0.03	$ (0.93)	$ (1.06)	$ (0.04)	$ 1.54
Earnings (loss) per share - Diluted (in dollars per share)	$ (0.13)	$ (0.96)	$ 0.02	$ 0.01	$ (0.06)	$ (0.01)	$ 0.02	$ 0.01	$ 0.03	$ (0.93)	$ (1.06)	$ (0.04)	$ 1.51
As Reported
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Total revenue		$ 20,852	$ 19,895	$ 17,991	$ 16,160	$ 16,396	$ 18,204	$ 14,718				$ 65,478	$ 67,693
Operating income (loss)		(13,561)	593	209	106	(44)	226	350				638	1,567
Net income (loss)		$ (12,232)	$ 573	$ 357	$ (282)	$ 236	$ 247	$ 225				$ 426	$ 19,851
Earnings (loss) per share - Basic (in dollars per share)		$ (0.93)	$ 0.04	$ 0.03	$ (0.02)	$ 0.02	$ 0.02	$ 0.02				$ 0.03	$ 1.55
Earnings (loss) per share - Diluted (in dollars per share)		$ (0.93)	$ 0.04	$ 0.03	$ (0.02)	$ 0.02	$ 0.02	$ 0.02				$ 0.03	$ 1.51
Revisions \| Revision Of Prior Period Financial Statements
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Total revenue		$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0				$ 0	$ 0
Operating income (loss)		(460)	(291)	(354)	(597)	(456)	(47)	(45)				(1,145)	(96)
Net income (loss)		$ (347)	$ (246)	$ (259)	$ (467)	$ (354)	$ (36)	$ (35)			$ 1,130	$ (892)	$ (57)
Earnings (loss) per share - Basic (in dollars per share)		$ (0.03)	$ (0.02)	$ (0.02)	$ (0.04)	$ (0.03)	$ 0	$ (0.01)				$ (0.07)	$ (0.01)
Earnings (loss) per share - Diluted (in dollars per share)		$ (0.03)	$ (0.02)	$ (0.02)	$ (0.04)	$ (0.03)	$ 0	$ (0.01)				$ (0.07)	$ 0

- Definition

The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04(19))
-URI http://asc.fasb.org/extlink&oid=116637232&loc=SL114874131-224263

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 45
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=117326831&loc=d3e1337-109256

Reference 3: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 55
-Paragraph 52
-URI http://asc.fasb.org/extlink&oid=117327953&loc=d3e4984-109258

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(21))
-URI http://asc.fasb.org/extlink&oid=116634182&loc=SL114868664-224227

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=109234566&loc=d3e22694-107794

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=6371337&loc=d3e3550-109257

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=117326831&loc=d3e1252-109256

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04(23))
-URI http://asc.fasb.org/extlink&oid=116637391&loc=SL114874048-224260

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 45
-Paragraph 60B
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=117326831&loc=SL5780133-109256

+ Details

- Definition

The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 55
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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-Name Accounting Standards Codification
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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Reference 4: http://www.xbrl.org/2003/role/disclosureRef
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Reference 5: http://www.xbrl.org/2003/role/disclosureRef
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Reference 6: http://www.xbrl.org/2003/role/disclosureRef
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Reference 7: http://www.xbrl.org/2003/role/disclosureRef
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-Name Accounting Standards Codification
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Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
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Reference 9: http://www.xbrl.org/2003/role/disclosureRef
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-Name Accounting Standards Codification
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-URI http://asc.fasb.org/extlink&oid=116637232&loc=SL114874131-224263

+ Details

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References + Details

Revisions of Prior Period Financial Statements (Narrative) (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Operating costs and expenses		$ 93,597	$ 65,985	$ 66,222
Minimum
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Rental arrangements, original term		6 months
Maximum
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Rental arrangements, original term		60 months
Revisions \| Revision Of Prior Period Financial Statements
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Operating costs and expenses	$ 1,100		$ 1,145	$ 96

Revisions of Prior Period Financial Statements (Revised Consolidated Balance Sheet) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Current Assets:
Inventory	$ 21,080	$ 30,190
Prepaid income taxes	40	3,188
Prepaid expenses and other	597	1,696
Total current assets	42,415	94,921
Rental equipment, net of accumulated depreciation	217,742	176,106
Property and equipment, net of accumulated depreciation	21,869	16,644
Total assets	286,577	304,200
LIABILITIES AND STOCKHOLDERS' EQUITY
Deferred income tax liability	31,243	31,906
Total liabilities	38,884	44,968
Stockholders’ Equity:
Retained earnings	137,478	151,342	$ 151,808
Total stockholders' equity	247,693	259,232	257,262	$ 232,954
Total liabilities and stockholders' equity	$ 286,577	304,200
As Reported
Current Assets:
Inventory		30,974
Prepaid income taxes		3,148
Prepaid expenses and other		2,430
Total current assets		96,399
Rental equipment, net of accumulated depreciation		175,886
Property and equipment, net of accumulated depreciation		16,587
Total assets		305,401
LIABILITIES AND STOCKHOLDERS' EQUITY
Deferred income tax liability		32,158
Total liabilities		45,220
Stockholders’ Equity:
Retained earnings		152,291	151,865
Total stockholders' equity		260,181	257,319
Total liabilities and stockholders' equity		305,401
Revisions \| Revision Of Prior Period Financial Statements
Current Assets:
Inventory		(784)
Prepaid income taxes		40
Prepaid expenses and other		(734)
Total current assets		(1,478)
Rental equipment, net of accumulated depreciation		220
Property and equipment, net of accumulated depreciation		57
Total assets		(1,201)
LIABILITIES AND STOCKHOLDERS' EQUITY
Deferred income tax liability		(252)
Total liabilities		(252)
Stockholders’ Equity:
Retained earnings		(949)	(57)
Total stockholders' equity		(949)	$ (57)
Total liabilities and stockholders' equity		$ (1,201)

Revisions of Prior Period Financial Statements (Revised Consolidated Statements of Income) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								6 Months Ended	9 Months Ended	12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Sep. 30, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenue:
Revenues	$ 19,706	$ 20,852	$ 19,895	$ 17,991	$ 16,160	$ 16,396	$ 18,204	$ 14,718			$ 78,444	$ 65,478	$ 67,693
Operating costs and expenses:
Cost of rentals, exclusive of depreciation stated separately below											27,583	21,860	18,160
Depreciation and amortization											23,268	22,080	21,316
Operating costs and expenses											93,597	65,985	66,222
Operating income (loss)	(1,289)	(14,021)	302	(145)	(491)	(500)	179	305			(15,153)	(507)	1,471
Income (loss) before provision for income taxes											(14,557)	(394)	1,507
(Provision for) benefit from income taxes:
Current											31	242	(3,288)
Deferred											662	(314)	21,575
Total income tax benefit (expense)											693	(72)	18,287
Net income (loss)	$ (1,710)	$ (12,579)	$ 327	$ 98	$ (749)	$ (118)	$ 211	$ 190			$ (13,864)	$ (466)	$ 19,794
Earnings Per Share [Abstract]
Earnings (loss) per share - Basic (in dollars per share)	$ (0.13)	$ (0.96)	$ 0.02	$ 0.01	$ (0.06)	$ (0.01)	$ 0.02	$ 0.01	$ 0.03	$ (0.93)	$ (1.06)	$ (0.04)	$ 1.54
Earnings (loss) per share - Diluted (in dollars per share)	$ (0.13)	$ (0.96)	$ 0.02	$ 0.01	$ (0.06)	$ (0.01)	$ 0.02	$ 0.01	$ 0.03	$ (0.93)	$ (1.06)	$ (0.04)	$ 1.51
As Reported
Revenue:
Revenues		$ 20,852	$ 19,895	$ 17,991	$ 16,160	$ 16,396	$ 18,204	$ 14,718				$ 65,478	$ 67,693
Operating costs and expenses:
Cost of rentals, exclusive of depreciation stated separately below												20,746	18,078
Depreciation and amortization												22,049	21,302
Operating costs and expenses												64,840	66,126
Operating income (loss)		(13,561)	593	209	106	(44)	226	350				638	1,567
Income (loss) before provision for income taxes												751	1,603
(Provision for) benefit from income taxes:
Current												248	(3,334)
Deferred												(573)	21,582
Total income tax benefit (expense)												(325)	18,248
Net income (loss)		$ (12,232)	$ 573	$ 357	$ (282)	$ 236	$ 247	$ 225				$ 426	$ 19,851
Earnings Per Share [Abstract]
Earnings (loss) per share - Basic (in dollars per share)		$ (0.93)	$ 0.04	$ 0.03	$ (0.02)	$ 0.02	$ 0.02	$ 0.02				$ 0.03	$ 1.55
Earnings (loss) per share - Diluted (in dollars per share)		$ (0.93)	$ 0.04	$ 0.03	$ (0.02)	$ 0.02	$ 0.02	$ 0.02				$ 0.03	$ 1.51
Revisions \| Revision Of Prior Period Financial Statements
Revenue:
Revenues		$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0				$ 0	$ 0
Operating costs and expenses:
Cost of rentals, exclusive of depreciation stated separately below												1,114	82
Depreciation and amortization												31	14
Operating costs and expenses										$ 1,100		1,145	96
Operating income (loss)		(460)	(291)	(354)	(597)	(456)	(47)	(45)				(1,145)	(96)
Income (loss) before provision for income taxes												(1,145)	(96)
(Provision for) benefit from income taxes:
Current												(6)	46
Deferred												259	(7)
Total income tax benefit (expense)												253	39
Net income (loss)		$ (347)	$ (246)	$ (259)	$ (467)	$ (354)	$ (36)	$ (35)			$ 1,130	$ (892)	$ (57)
Earnings Per Share [Abstract]
Earnings (loss) per share - Basic (in dollars per share)		$ (0.03)	$ (0.02)	$ (0.02)	$ (0.04)	$ (0.03)	$ 0	$ (0.01)				$ (0.07)	$ (0.01)
Earnings (loss) per share - Diluted (in dollars per share)		$ (0.03)	$ (0.02)	$ (0.02)	$ (0.04)	$ (0.03)	$ 0	$ (0.01)				$ (0.07)	$ 0

Revisions of Prior Period Financial Statements (Revised Consolidated Statements of Stockholders' Equity) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net income (loss)	$ (1,710)	$ (12,579)	$ 327	$ 98	$ (749)	$ (118)	$ 211	$ 190	$ (13,864)	$ (466)	$ 19,794
Retained earnings	137,478				151,342				137,478	151,342	151,808
Total stockholders' equity	$ 247,693				259,232				247,693	259,232	257,262	$ 232,954
As Reported
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net income (loss)		(12,232)	573	357	(282)	236	247	225		426	19,851
Retained earnings					152,291					152,291	151,865
Total stockholders' equity					260,181					260,181	257,319
Revisions \| Revision Of Prior Period Financial Statements
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net income (loss)		$ (347)	$ (246)	$ (259)	(467)	$ (354)	$ (36)	$ (35)	$ 1,130	(892)	(57)
Retained earnings					(949)					(949)	(57)
Total stockholders' equity					$ (949)					$ (949)	$ (57)

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References + Details

Revisions of Prior Period Financial Statements (Revised Consolidated Statements of Cash Flows) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income (loss)	$ (1,710)	$ (12,579)	$ 327	$ 98	$ (749)	$ (118)	$ 211	$ 190	$ (13,864)	$ (466)	$ 19,794
Depreciation and amortization									23,268	22,080	21,316
Deferred taxes									(662)	314	(21,575)
Inventory (increase) decrease									8,256	(5,102)	(5,221)
Prepaid income taxes and prepaid expenses (increase) decrease									3,288	(578)	(1,852)
Net cash provided by operating activities									29,412	23,689	17,499
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchase of rental equipment, property and other equipment									(69,938)	(40,065)	(13,536)
Net cash used in investing activities									(70,175)	(40,285)	(12,838)
Net change in cash and cash equivalents									(41,036)	(16,580)	5,114
As Reported
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income (loss)		(12,232)	573	357	(282)	236	247	225		426	19,851
Depreciation and amortization										22,049	21,302
Deferred taxes										573	(21,582)
Inventory (increase) decrease										(5,757)	(5,350)
Prepaid income taxes and prepaid expenses (increase) decrease										(1,318)	(1,806)
Net cash provided by operating activities										23,414	17,452
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchase of rental equipment, property and other equipment										(39,790)	(13,489)
Net cash used in investing activities										(40,010)	(12,791)
Net change in cash and cash equivalents										(16,580)	5,114
Revisions \| Revision Of Prior Period Financial Statements
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income (loss)		$ (347)	$ (246)	$ (259)	$ (467)	$ (354)	$ (36)	$ (35)	$ 1,130	(892)	(57)
Depreciation and amortization										31	14
Deferred taxes										(259)	7
Inventory (increase) decrease										655	129
Prepaid income taxes and prepaid expenses (increase) decrease										740	(46)
Net cash provided by operating activities										275	47
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchase of rental equipment, property and other equipment										(275)	(47)
Net cash used in investing activities										(275)	(47)
Net change in cash and cash equivalents										$ 0	$ 0