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Document and Entity Information - shares	3 Months Ended
Document and Entity Information - shares	Mar. 31, 2018	May 04, 2018
Document and Entity Information [Abstract]
Entity Registrant Name	NATURAL GAS SERVICES GROUP INC
Entity Central Index Key	0001084991
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Document Type	10-Q
Document Period End Date	Mar. 31, 2018
Document Fiscal Year Focus	2018
Document Fiscal Period Focus	Q1
Amendment Flag	false
Entity Common Stock, Shares Outstanding		13,085,607

Condensed Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Current Assets:
Cash and cash equivalents	$ 65,138	$ 69,208
Trade accounts receivable, net of allowance for doubtful accounts of $495 and $569, respectively	7,719	8,534
Inventory	25,749	26,224
Prepaid income taxes	3,443	3,443
Prepaid expenses and other	329	817
Total current assets	102,378	108,226
Long-term inventory, net of allowance for obsolescence of $21 and $15, respectively	3,315	2,829
Rental equipment, net of accumulated depreciation of $150,859 and $145,851, respectively	168,790	167,099
Property and equipment, net of accumulated depreciation of $11,528 and $11,274, respectively	9,277	7,652
Goodwill	10,039	10,039
Intangibles, net of accumulated amortization of $1,664 and $1,632, respectively	1,495	1,526
Other assets	1,066	939
Total assets	296,360	298,310
Current Liabilities:
Accounts payable	1,322	4,162
Accrued liabilities	3,407	3,106
Deferred income	294	185
Total current liabilities	5,023	7,453
Line of credit, non-current portion	417	417
Deferred income tax liability	32,211	32,163
Other long-term liabilities	1,075	958
Total liabilities	38,726	40,991
Commitments and contingencies (Note 8)
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; 12,949 and 12,880 shares issued and outstanding, respectively	129	129
Additional paid-in capital	105,415	105,325
Retained earnings	152,090	151,865
Deferred compensation liability payable in company stock	816	0
Company stock held by deferred compensation plan	(816)	0
Total stockholders' equity	257,634	257,319
Total liabilities and stockholders' equity	$ 296,360	$ 298,310

Condensed Consolidated Balance Sheets (Unaudited) (Parentheticals) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Current Assets:
Allowance for doubtful accounts	$ 495	$ 569
Allowance for inventory obsolescence	21	15
Noncurrent Assets:
Accumulated depreciation, rental equipment	150,859	145,851
Accumulated depreciation, property and equipment	11,528	11,274
Accumulated amortization, intangibles	$ 1,664	$ 1,632
Stockholders’ Equity:
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value (in USD per share)	$ 0.01	$ 0.01
Common stock, shares authorized	30,000,000	30,000,000
Common stock, shares issued	12,949,000	12,880,000
Common stock, shares outstanding	12,949,000	12,880,000

Condensed Consolidated Income Statements (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Revenue:
Rental income	$ 11,471	$ 11,922
Sales	2,998	6,637
Service and maintenance income	249	343
Total revenue	14,718	18,902
Operating costs and expenses:
Cost of rentals, exclusive of depreciation stated separately below	4,704	4,668
Cost of sales, exclusive of depreciation stated separately below	2,191	5,423
Cost of service and maintenance	65	94
Selling, general and administrative expense	2,021	3,046
Depreciation and amortization	5,387	5,328
Total operating costs and expenses	14,368	18,559
Operating income	350	343
Other income (expense):
Interest expense	(3)	(2)
Other (expense) income , net	(73)	3
Total other (expense) income, net	(76)	1
Income before provision for income taxes	274	344
Provision for income taxes	49	92
Net income	$ 225	$ 252
Earnings per share:
Basic (in USD per share)	$ 0.02	$ 0.02
Diluted (in USD per share)	$ 0.02	$ 0.02
Weighted average shares outstanding:
Basic (in shares)	12,920	12,804
Diluted (in shares)	13,169	13,056

Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 225	$ 252
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	5,387	5,328
Deferred income taxes	48	(1,266)
Stock-based compensation	428	1,532
Bad debt allowance	(50)	60
Gain on sale of assets	0	(27)
Loss (gain) on company owned life insurance	67	(12)
Changes in operating assets and liabilities:
Trade accounts receivables	865	2,637
Inventory	15	1,661
Prepaid expenses and prepaid income taxes	488	1,930
Accounts payable and accrued liabilities	(2,539)	68
Deferred income	109	(1,741)
Other	85	43
NET CASH PROVIDED BY OPERATING ACTIVITIES	5,128	10,465
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchase of rental equipment and property and equipment	(8,712)	(144)
Purchase of company owned life insurance	(139)	(93)
Proceeds from sale of property and equipment	0	27
NET CASH USED IN INVESTING ACTIVITIES	(8,851)	(210)
CASH FLOWS FROM FINANCING ACTIVITIES:
Payments from other long-term liabilities, net	(9)	(4)
Proceeds from exercise of stock options	157	517
Taxes paid related to net share settlement of equity awards	(495)	(492)
NET CASH (USED IN) PROVIDED BY FINANCING ACTIVITIES	(347)	21
NET CHANGE IN CASH AND CASH EQUIVALENTS	(4,070)	10,276
CASH AND CASH EQUIVALENTS AT BEGINNING OF PERIOD	69,208	64,094
CASH AND CASH EQUIVALENTS AT END OF PERIOD	65,138	74,370
SUPPLEMENTAL DISCLOSURE OF CASH FLOW INFORMATION:
Interest paid	3	2
Income taxes paid	0	0
NON-CASH TRANSACTIONS
Transfer of rental equipment components to inventory	$ 40	$ 48

Basis of Presentation and Summary of Significant Accounting Policies

3 Months Ended

Mar. 31, 2018

Accounting Policies [Abstract]

Basis of Presentation and Summary of Significant Accounting Policies

These notes apply to the unaudited condensed consolidated financial statements of Natural Gas Services Group, Inc. a Colorado corporation (the "Company", “NGSG”, "Natural Gas Services Group", "we" or "our").

The accompanying unaudited condensed consolidated financial statements include all adjustments, consisting of only normal recurring adjustments, which are necessary to make our financial position at March 31, 2018 and the results of our operations for the three months ended March 31, 2018 and 2017 not misleading. As permitted by the rules and regulations of the Securities and Exchange Commission (SEC), the accompanying condensed consolidated financial statements do not include all disclosures normally required by generally accepted accounting principles in the United States of America (GAAP). These financial statements should be read in conjunction with the financial statements included in our Annual Report on Form 10-K for the year ended December 31, 2017 on file with the SEC. In our opinion, the condensed consolidated financial statements are a fair presentation of the financial position, results of operations and cash flows for the periods presented.

The results of operations for the three months ended March 31, 2018 are not necessarily indicative of the results of operations to be expected for the full fiscal year ending December 31, 2018.

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. If an adjustment had been needed, we would have recognized the cumulative effect of initially applying ASC 606 with an adjustment to the opening balance of equity at January 1, 2018. Therefore, 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). We recognize revenue once a performance obligation has been satisfied and control over a product or service has transferred to the customer. Shipping and handling costs incurred are accounted for as fulfillment costs and are included in cost of revenues in our condensed consolidated income statement.

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 may also include a fee for servicing the compressor or flare during the rental contract. Our rental contracts range from six to twenty-four months, with revenue being recognized over time, in equal 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 with generally accepted accounting principles, the revenue earned from servicing rental equipment is recognized in accordance with ASC 606, while the revenue earned from the rental of the equipment is recognized in accordance with ASC 840 - Leases.

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 complete 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 customer’s 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 condensed 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, title of the equipment, all risk of ownership including, the risk of loss, 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 risks of loss are shouldered by the customer, and there are no exceptions to the customer’s commitment to accept and pay for the manufactured equipment. Revenues recognized at the completion of manufacturing for the three months ended March 31, 2018 was approximately $1.7 million.

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 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, 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 three moths ended March 31, 2018 and 2017:



	Three months ended March 31,
	(in thousands)
	2018		2017
Compressors - sales	$	1,829	$	5,640
Flares - sales	522		269
Other (Parts/Rebuilds) - sales	647		727
Service and maintenance ¹	4,837		5,116
Total revenue from contracts with customers	7,835		11,752
Add: non-ASC 606 rental revenue	6,883		7,150
Total revenue	$	14,718	$	18,902

¹Service and maintenance includes revenue from servicing our own rental equipment contracted to customers and third party equipment.

Contract Balances

As of March 31, 2018 and December 31, 2017, we had the following receivables and deferred income from contracts with customers:



	March 31, 2018			December 31, 2017
	(in thousands)
Accounts Receivable
Accounts receivable - contracts with customers	$	5,080		$	5,454
Accounts receivable - non-ASC 606	3,134			3,649
Total Accounts Receivable	$	8,214		$	9,103
Less:Allowance for doubtful accounts	$	(495	)	$	(569	)
Total Accounts Receivable, net	$	7,719		$	8,534

Deferred income	$	294		$	185

The Company did not recognize any revenue for the period ended March 31, 2018 that were included in deferred income at the beginning of the period. For the period ended December 31, 2017, the Company recognized revenue of $1.9 million from amounts related to sales that were included in deferred income at the beginning of the period.

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

The following table includes estimated revenue expected to be recognized in the future related to performance obligations that are unsatisfied (or partially unsatisfied) at the end of the reporting period:



(in thousands)	2019⁽¹⁾		2020		2021		2022		2023		Total
Service and Maintenance	$	610	$	595	$	542	$	542	$	9	$	2,298

(1) For the nine months starting April 2019.

All consideration from contracts with customers is included in the amounts presented above.

The Company applies the practical expedient in ASC 606-10-50-14 and does not disclose information about remaining performance obligations that have original expected durations of one year or less.

The Company applies the transition practical expedient in ASC 606-10-65-1(f)(3) and does not disclose the amount of the transaction price allocated to the remaining performance obligations and an explanation of when the Company expects to recognize that amount as revenue for 2017.

Contract Costs

The Company applies the practical expedient in ASC 340-40-25-4 and 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 income statement.

Fair Value of Financial Instruments

Our financial instruments consist principally of cash and cash equivalents, accounts receivable, accounts payable, deferred compensation plan (cash portion) and our line of credit. Pursuant to ASC 820 (Accounting Standards Codification), the fair value of our cash equivalents is determined based on “Level 1” inputs, which consist of quoted prices in active markets for identical assets. We believe that the recorded values of all of our other financial instruments approximate their fair values because of their nature and relatively short maturity dates or durations.

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.

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. We have no uncertain tax positions as of March 31, 2018.

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

On December 22, 2017, the U.S. government enacted comprehensive tax legislation commonly referred to as the Tax Cuts and Jobs Act (the “2017 Tax Act”), which makes broad and complex changes to the U.S. tax code. Certain income tax effects of the 2017 Tax Act are reflected in the Company’s financial results in accordance with Staff Accounting Bulletin No. 118 (“SAB 118”), which provides SEC staff guidance regarding the application of Accounting Standards Codification Topic 740 Income Taxes (“ASC 740”). As we do not have all of the necessary information to analyze all income tax effects of the 2017 Tax Act, we will continue to evaluate tax reform and adjust the provisional amounts as additional information is obtained. We expect to complete our detailed analysis no later than the fourth quarter of 2018.

Recently Issued Accounting Pronouncements

On February 25, 2016, the Financial Accounting Standards Board ("FASB") issued ASU No. 2016-02, Leases (Topic 842). Under the new guidance, a lessee will be required to recognize assets and liabilities for capital and operating leases with lease terms of more than 12 months. Additionally, this ASU will require disclosures to help investors and other financial statement users better understand the amount, timing, and uncertainty of cash flows arising from leases, including qualitative and quantitative requirements. For public business entities, the amendments are effective for fiscal years beginning after December 15, 2018, including interim periods within those fiscal years, with early adoption permitted. The new standard will be effective during our first quarter ending March 31, 2019. The process of reviewing our leases and evaluating the impact of the new standard on our condensed consolidated financial statements and disclosures is ongoing, but we expect our review to be completed in the latter half of 2018.

Reclassification of Prior Period Balances

Certain reclassifications have been made to prior period amounts to conform to the current-year presentation. These

reclassifications had no effect on the reported results of operations.

Stock-Based Compensation

3 Months Ended

Mar. 31, 2018

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Stock-Based Compensation

Stock Options:

A summary of option activity under our 1998 Stock Option Plan as of December 31, 2017, and changes during the three months ended March 31, 2018 is presented below.



	Number of Stock Options		Weighted Average Exercise Price		Weighted Average Remaining Contractual Life (years)	Aggregate Intrinsic Value (in thousands)
Outstanding, December 31, 2017	327,270		$	20.21	4.28	$	2,255
Exercised	(8,500	)	18.51			86
Outstanding, March 31, 2018	318,770		$	20.25	4.07	$	1,638
Exercisable, March 31, 2018	296,738		$	19.67	3.72	$	1,638

The following table summarizes information about our stock options outstanding at March 31, 2018:



Range of Exercise Prices	Options Outstanding				Options Exercisable
Range of Exercise Prices	Shares	Weighted Average Remaining Contractual Life (years)	Weighted Average Exercise Price		Shares	Weighted Average Exercise Price
$0.01-15.70	65,852	1.31	$	9.82	65,852	$	9.82
$15.71-17.81	67,750	1.62	17.53		67,750	17.53
$17.82-20.48	54,250	3.22	19.39		54,250	19.39
$20.49-33.36	130,918	7.09	27.27		108,886	27.09
	318,770	4.07	$	20.25	296,738	$	19.67

The summary of the status of our unvested stock options as of December 31, 2017 and changes during the three months ended March 31, 2018 is presented below.



Unvested stock options:	Shares		Weighted Average Grant Date Fair Value Per Share
Unvested at December 31, 2017	48,581		$	11.41
Vested	(26,549	)	10.97
Unvested at March 31, 2018	22,032		$	11.93

As of March 31, 2018, there was $223,511 of unrecognized compensation cost related to unvested options. Such cost is expected to be recognized over a weighted-average period of two years. Total compensation expense for stock options was $66,625 and $124,331 for the three months ended March 31, 2018 and 2017, respectively.

Restricted Shares/Units:

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 2017 performance, Mr. Taylor, was awarded 84,700 restricted shares/units on March 15, 2018, which vest over three years, in equal installments, beginning March 15, 2019. On March 15, 2018, the Compensation Committee awarded 20,000 restricted shares/units to each of G. Larry Lawrence, our CFO, and James Hazlett, our Vice President of Technical Services. The restricted shares to Messrs. Lawrence and Hazlett vest over three years, in equal installments, beginning March 15, 2019. We also awarded and issued 16,288 shares of restricted common stock to the independent members of our Board of Directors as partial payment for 2018 services as directors. The restricted stock issued to our directors vests over one year, in quarterly installments, beginning March 31, 2019. Total compensation expense related to restricted awards was $361,630 and $1,408,265 for the three months ended March 31, 2018 and 2017, respectively. As of March 31, 2018, there was a total of $4,408,825 of unrecognized compensation expense related to these shares/units which is expected to be recognized over the next three years.

Inventory

3 Months Ended

Mar. 31, 2018

Inventory Disclosure [Abstract]

Inventory

Our inventory, net of allowance for obsolescence of $20,785 and $15,000 at March 31, 2018 and December 31, 2017, respectively, consisted of the following amounts:



	March 31, 2018		December 31, 2017
	(in thousands)
Raw materials - current	$	21,482	$	22,813
Raw materials - long term	3,315		2,829
Finished Goods	1,022		1,022
Work in process	3,245		2,389
	$	29,064	$	29,053

Our long-term inventory consists of raw materials that remain viable but that the Company does not expect to sell within the year.

During the three months ended March 31, 2018 and 2017, there were no write-offs of obsolete inventory against the allowance for obsolescence.

Deferred Compensation Plans	3 Months Ended
Deferred Compensation Plans	Mar. 31, 2018
Postemployment Benefits [Abstract]
Deferred Compensation Plans	Deferred Compensation Plans The Company has 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 of up to 90% of a participant’s base salary, bonus, commissions, director fees and restricted stock unit 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 $966,000 and $312,000 as of March 31, 2018 and 2017, respectively. For the three months ending March 31, 2018, we reported in other (expense) income in the consolidated income statement a loss related to the policy of approximately $67,000 and for the same period in 2017, a gain of approximately $12,000. 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 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 $992,000 and $261,000 as of March 31, 2018 and 2017, respectively. The deferred obligation is included in other long-term liabilities in the condensed 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 March 31, 2018, 104,590 unvested restricted stock units have been deferred and 32,037 units have been released; carrying a value of $816,373 to the deferred compensation plan.

Credit Facility	3 Months Ended
Credit Facility	Mar. 31, 2018
Debt Disclosure [Abstract]
Credit Facility	Credit Facility We have a senior secured revolving credit agreement the ("Amended Credit Agreement") with JP Morgan Chase Bank, N.A (the "Lender") with an 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). On August 31, 2017, we amended and renewed the Amended Credit Agreement, which was set to expire on December 31, 2017. The Credit Agreement Amendment extended the maturity date to December 31, 2020. No other material revisions were made to the credit facility. 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. 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 March 31, 2018 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 1.50%. For the three month period ended March 31, 2018, our weighted average interest rate was 3.16%. 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 leases receivables, along with a first priority lien on a variable number of our leased compressor equipment the book value of which 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 on a consolidated basis 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 March 31, 2018, 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 March 31, 2018 and December 31, 2017 our outstanding balance on the line of credit was $417,000.

Earnings per Share

3 Months Ended

Mar. 31, 2018

Earnings Per Share [Abstract]

Earnings per Share

The following table reconciles the numerators and denominators of the basic and diluted earnings per share computation(in thousands, except per share data):



	Three months ended
	March 31,
	2018		2017
Numerator:
Net income	$	225	$	252
Denominator for basic net income per common share:
Weighted average common shares outstanding	12,920		12,804
Denominator for diluted net income per share:
Weighted average common shares outstanding	12,920		12,804
Dilutive effect of stock options and restricted stock	249		252
Diluted weighted average shares	13,169		13,056
Earnings per common share:
Basic	$	0.02	$	0.02
Diluted	$	0.02	$	0.02

In the three months ended March 31, 2018 and 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 antidilutive effect.

Segment Information

3 Months Ended

Mar. 31, 2018

Segment Reporting [Abstract]

Segment Information

ASC 280-10-50, “Operating Segments", defines 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 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 and crude oil. 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.



For the three months ended March 31, 2018 (in thousands):
	Rental		Sales		Service & Maintenance		Corporate			Total
Revenue	$	11,471	$	2,998	$	249	$	—		$	14,718
Operating costs and corporate expenses	4,704		2,191		65		7,408			14,368
Total other expense, net	—		—		—		(76		)	(76		)
Income before provision for income taxes	$	6,767	$	807	$	184	$	(7,484	)	$	274



For the three months ended March 31, 2017 (in thousands):
	Rental		Sales		Service & Maintenance		Corporate			Total
Revenue	$	11,922	$	6,637	$	343	$	—		$	18,902
Operating costs and corporate expenses	4,668		5,423		94		8,374			18,559
Total other income, net	—		—		—		1			1
Income before provision for income taxes	$	7,254	$	1,214	$	249	$	(8,373	)	$	344

Commitments and Contingencies	3 Months Ended
Commitments and Contingencies	Mar. 31, 2018
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies 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 adverse effect on our financial position, results of operations or cash flow. We are not currently a party to any material legal proceedings, and we are not aware of any threatened material litigation. The Company also has a contractual obligation related to the construction of a new corporate office of approximately $10.5 million, financed by cash on hand. Construction of a new office began in late 2017 and is expected to be completed in early 2019.

Basis of Presentation and Summary of Significant Accounting Policies (Policies)

3 Months Ended

Mar. 31, 2018

Accounting Policies [Abstract]

Basis of Accounting

The results of operations for the three months ended March 31, 2018 are not necessarily indicative of the results of operations to be expected for the full fiscal year ending December 31, 2018.

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.

Fair Value of Financial Instruments

Recently Issued Accounting Pronouncements

Segment 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.

Basis of Presentation and Summary of Significant Accounting Policies - (Tables)

3 Months Ended

Mar. 31, 2018

Accounting Policies [Abstract]

Disaggregation of Revenue

The following table shows the Company's revenue disaggregated by product or service type for the three moths ended March 31, 2018 and 2017:



	Three months ended March 31,
	(in thousands)
	2018		2017
Compressors - sales	$	1,829	$	5,640
Flares - sales	522		269
Other (Parts/Rebuilds) - sales	647		727
Service and maintenance ¹	4,837		5,116
Total revenue from contracts with customers	7,835		11,752
Add: non-ASC 606 rental revenue	6,883		7,150
Total revenue	$	14,718	$	18,902

¹Service and maintenance includes revenue from servicing our own rental equipment contracted to customers and third party equipment.

Schedule of Contract with Customer, Asset and Liability



	March 31, 2018			December 31, 2017
	(in thousands)
Accounts Receivable
Accounts receivable - contracts with customers	$	5,080		$	5,454
Accounts receivable - non-ASC 606	3,134			3,649
Total Accounts Receivable	$	8,214		$	9,103
Less:Allowance for doubtful accounts	$	(495	)	$	(569	)
Total Accounts Receivable, net	$	7,719		$	8,534

Deferred income	$	294		$	185

Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction



(in thousands)	2019⁽¹⁾		2020		2021		2022		2023		Total
Service and Maintenance	$	610	$	595	$	542	$	542	$	9	$	2,298

(1) For the nine months starting April 2019.

Stock-Based Compensation (Tables)

3 Months Ended

Mar. 31, 2018

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Summary of Option Activity

A summary of option activity under our 1998 Stock Option Plan as of December 31, 2017, and changes during the three months ended March 31, 2018 is presented below.



	Number of Stock Options		Weighted Average Exercise Price		Weighted Average Remaining Contractual Life (years)	Aggregate Intrinsic Value (in thousands)
Outstanding, December 31, 2017	327,270		$	20.21	4.28	$	2,255
Exercised	(8,500	)	18.51			86
Outstanding, March 31, 2018	318,770		$	20.25	4.07	$	1,638
Exercisable, March 31, 2018	296,738		$	19.67	3.72	$	1,638

Summary of Stock Options Outstanding

The following table summarizes information about our stock options outstanding at March 31, 2018:



Range of Exercise Prices	Options Outstanding				Options Exercisable
Range of Exercise Prices	Shares	Weighted Average Remaining Contractual Life (years)	Weighted Average Exercise Price		Shares	Weighted Average Exercise Price
$0.01-15.70	65,852	1.31	$	9.82	65,852	$	9.82
$15.71-17.81	67,750	1.62	17.53		67,750	17.53
$17.82-20.48	54,250	3.22	19.39		54,250	19.39
$20.49-33.36	130,918	7.09	27.27		108,886	27.09
	318,770	4.07	$	20.25	296,738	$	19.67

Status of Unvested Stock Options

The summary of the status of our unvested stock options as of December 31, 2017 and changes during the three months ended March 31, 2018 is presented below.



Unvested stock options:	Shares		Weighted Average Grant Date Fair Value Per Share
Unvested at December 31, 2017	48,581		$	11.41
Vested	(26,549	)	10.97
Unvested at March 31, 2018	22,032		$	11.93

Inventory (Tables)

3 Months Ended

Mar. 31, 2018

Inventory Disclosure [Abstract]

Schedule of Inventory

Our inventory, net of allowance for obsolescence of $20,785 and $15,000 at March 31, 2018 and December 31, 2017, respectively, consisted of the following amounts:



	March 31, 2018		December 31, 2017
	(in thousands)
Raw materials - current	$	21,482	$	22,813
Raw materials - long term	3,315		2,829
Finished Goods	1,022		1,022
Work in process	3,245		2,389
	$	29,064	$	29,053

Earnings per Share (Tables)

3 Months Ended

Mar. 31, 2018

Earnings Per Share [Abstract]

Schedule of Earnings Per Share, Basic and Diluted

The following table reconciles the numerators and denominators of the basic and diluted earnings per share computation(in thousands, except per share data):



	Three months ended
	March 31,
	2018		2017
Numerator:
Net income	$	225	$	252
Denominator for basic net income per common share:
Weighted average common shares outstanding	12,920		12,804
Denominator for diluted net income per share:
Weighted average common shares outstanding	12,920		12,804
Dilutive effect of stock options and restricted stock	249		252
Diluted weighted average shares	13,169		13,056
Earnings per common share:
Basic	$	0.02	$	0.02
Diluted	$	0.02	$	0.02

Segment Information (Tables)

3 Months Ended

Mar. 31, 2018

Segment Reporting [Abstract]

Schedule of Segment Reporting Information



For the three months ended March 31, 2018 (in thousands):
	Rental		Sales		Service & Maintenance		Corporate			Total
Revenue	$	11,471	$	2,998	$	249	$	—		$	14,718
Operating costs and corporate expenses	4,704		2,191		65		7,408			14,368
Total other expense, net	—		—		—		(76		)	(76		)
Income before provision for income taxes	$	6,767	$	807	$	184	$	(7,484	)	$	274



For the three months ended March 31, 2017 (in thousands):
	Rental		Sales		Service & Maintenance		Corporate			Total
Revenue	$	11,922	$	6,637	$	343	$	—		$	18,902
Operating costs and corporate expenses	4,668		5,423		94		8,374			18,559
Total other income, net	—		—		—		1			1
Income before provision for income taxes	$	7,254	$	1,214	$	249	$	(8,373	)	$	344

Basis of Presentation and Summary of Significant Accounting Policies (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Revenue from External Customer [Line Items]
Revenue	$ 14,718	$ 18,902
Bill and Hold Arrangement
Revenue from External Customer [Line Items]
Revenue	$ 1,700

Basis of Presentation and Summary of Significant Accounting Policies Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Disaggregation of Revenue [Line Items]
Revenue from contract with customer, excluding assessed tax	$ 7,835	$ 11,752
Rental revenue	6,883	7,150
Revenue	14,718	18,902
Compressors
Disaggregation of Revenue [Line Items]
Revenue from contract with customer, excluding assessed tax	1,829	5,640
Flares
Disaggregation of Revenue [Line Items]
Revenue from contract with customer, excluding assessed tax	522	269
Service & Maintenance
Disaggregation of Revenue [Line Items]
Revenue from contract with customer, excluding assessed tax	4,837	5,116
Revenue	249	343
Other (Parts/Rebuilds)
Disaggregation of Revenue [Line Items]
Revenue from contract with customer, excluding assessed tax	$ 4,837	$ 5,116

Basis of Presentation and Summary of Significant Accounting Policies Contract Balances (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Contract Assets
Increases due to cash received, excluding amounts recognized as revenue during the period	$ 0
Transferred to receivables from contract assets recognized at the beginning of the period	0
Contract Liabilities
Revenue Recognized that was included in the contract liability balance at the beginning of the year
Increases due to cash received, excluding amounts recognized as revenue during the period

Basis of Presentation and Summary of Significant Accounting Policies Transaction Price Allocated to the Remaining Performance Obligations (Details) $ in Thousands	Mar. 31, 2018 USD ($)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-04-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Compressor Related	$ 610
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Compressor Related	595
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Compressor Related	542
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Compressor Related	542
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Compressor Related	9
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: (nil)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Compressor Related	$ 2,298

Stock-Based Compensation - Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Number of Stock Options
Outstanding, beginning of period (in shares)	327,270
Exercised (in shares)	(8,500)
Outstanding, end of period (in shares)	318,770	327,270
Exercisable (in shares)	296,738
Weighted Average Exercise Price
Outstanding, beginning of period (in USD per share)	$ 20.21
Exercised (in USD per share)	18.51
Outstanding, end of period (in USD per share)	20.25	$ 20.21
Exercisable (in USD per share)	$ 19.67
Weighted Average Remaining Contractual Life (years)
Outstanding	4 years 25 days	4 years 2 months 42 days
Exercisable	3 years 7 months 50 days
Aggregate Intrinsic Value
Outstanding, beginning of period	$ 2,255
Exercised	86
Outstanding, end of period	1,638	$ 2,255
Exercisable	$ 1,638

Stock-Based Compensation - Stock Options Outstanding (Details)	3 Months Ended
	Mar. 31, 2018 $ / shares shares
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options outstanding, shares \| shares	318,770
Options outstanding, weighted average remaining contractual life (years)	4 years 25 days
Options outstanding, weighted average exercise price (in USD per share)	$ 20.25
Options exercisable, shares \| shares	296,738
Options exercisable, weighted average exercise price (in USD per share)	$ 19.67
$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 USD per share)	0.01
Range of exercise prices, upper limit (in USD per share)	$ 15.70
Options outstanding, shares \| shares	65,852
Options outstanding, weighted average remaining contractual life (years)	1 year 3 months 21 days
Options outstanding, weighted average exercise price (in USD per share)	$ 9.82
Options exercisable, shares \| shares	65,852
Options exercisable, weighted average exercise price (in USD per share)	$ 9.82
$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 USD per share)	15.71
Range of exercise prices, upper limit (in USD per share)	$ 17.81
Options outstanding, shares \| shares	67,750
Options outstanding, weighted average remaining contractual life (years)	1 year 6 months 44 days
Options outstanding, weighted average exercise price (in USD per share)	$ 17.53
Options exercisable, shares \| shares	67,750
Options exercisable, weighted average exercise price (in USD per share)	$ 17.53
$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 USD per share)	17.82
Range of exercise prices, upper limit (in USD per share)	$ 20.48
Options outstanding, shares \| shares	54,250
Options outstanding, weighted average remaining contractual life (years)	3 years 2 months 20 days
Options outstanding, weighted average exercise price (in USD per share)	$ 19.39
Options exercisable, shares \| shares	54,250
Options exercisable, weighted average exercise price (in USD per share)	$ 19.39
$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 USD per share)	20.49
Range of exercise prices, upper limit (in USD per share)	$ 33.36
Options outstanding, shares \| shares	130,918
Options outstanding, weighted average remaining contractual life (years)	7 years 34 days
Options outstanding, weighted average exercise price (in USD per share)	$ 27.27
Options exercisable, shares \| shares	108,886
Options exercisable, weighted average exercise price (in USD per share)	$ 27.09

Stock-Based Compensation - Summary of Unvested Stock Options (Details) - USD ($)	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Shares
Unvested, beginning of period (in shares)	48,581
Vested (in shares)	(26,549)
Unvested, end of period (in shares)	22,032
Weighted Average Grant Date Fair Value Per Share
Unvested, weighted average grant date fair value, beginning of period (in USD per share)	$ 11.41
Vested, weighted average grant date fair value (in USD per share)	10.97
Unvested, weighted average grant date fair value, end of period (in USD per share)	$ 11.93
Stock Options
Weighted Average Grant Date Fair Value Per Share
Unrecognized compensation cost related to unvested options	$ 223,511
Unrecognized compensation cost related to awards, weighted average period for recognition	2 years
Share-based compensation expense	$ 66,625	$ 124,331

Stock-Based Compensation - Restricted Stock (Details) - Restricted Stock - USD ($)			3 Months Ended
	Mar. 15, 2018	Feb. 14, 2017	Mar. 31, 2018	Mar. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense			$ 361,630	$ 1,408,265
Total unrecognized compensation expense			$ 4,408,825
Unrecognized compensation cost related to awards, vesting period			3 years
Chief Executive Officer
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grants in period (in shares)		84,700
Award vesting period		3 years
Chief Financial Officer
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grants in period (in shares)	20,000
Award vesting period	3 years
Vice President of Technical Services
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grants in period (in shares)	20,000
Award vesting period	3 years
Directors
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grants in period (in shares)			16,288
Award vesting period			1 year

Inventory (Details) - USD ($)	3 Months Ended
Inventory (Details) - USD ($)	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Inventory Disclosure [Abstract]
Allowance for inventory obsolescence	$ 21,000		$ 15,000
Raw materials - current	21,482,000		22,813,000
Raw materials - long term	3,315,000		2,829,000
Finished Goods	1,022,000		1,022,000
Work in process	3,245,000		2,389,000
Inventory, net	29,064,000		$ 29,053,000
Write-offs of obsolete inventory against allowance	$ 0	$ 0

Deferred Compensation Plans (Details) - USD ($)	3 Months Ended
Deferred Compensation Plans (Details) - USD ($)	Mar. 31, 2018	Mar. 31, 2017
Postemployment Benefits [Abstract]
Participant's maximum compensation deferral percentage	90.00%
Company owned life insurance	$ 966,000	$ 312,000
Loss (gain) on company owned life insurance	67,000	(12,000)
Deferred compensation obligation	$ 992,000	$ 261,000
Deferred restricted stock shares	104,590
Deferred compensation arrangement with individual, shares issued (in shares)	32,037
Deferred compensation arrangement, fair value of shares issued	$ 816,373

Credit Facility (Details)	3 Months Ended
Credit Facility (Details)	Mar. 31, 2018 USD ($) loan	Dec. 31, 2017 USD ($)
Line of Credit Facility [Line Items]
Line of credit, non-current portion	$ 417,000	$ 417,000
Revolving Credit Facility
Line of Credit Facility [Line Items]
Aggregate credit agreement commitment	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
Weighted average interest rate	3.16%
Default trigger, certain defaults of other company indebtedness, amount	$ 50,000
Default trigger, rendering of certain judgments, amount	150,000
Line of credit balance	$ 417,000
Line of credit, non-current portion		$ 417,000
LIBOR Rate \| Revolving Credit Facility
Line of Credit Facility [Line Items]
Reference rate, number of allowable LIBOR-based borrowings outstanding \| loan	3
Variable rate, applicable margin	1.50%
CB Floating Rate \| Revolving Credit Facility
Line of Credit Facility [Line Items]
Variable rate, applicable margin	1.50%
Minimum \| Revolving Credit Facility
Line of Credit Facility [Line Items]
Minimum commitment coverage ratio allowed	2.00
Maximum \| Revolving Credit Facility
Line of Credit Facility [Line Items]
Maximum leverage ratio allowed	2.50

Earnings per Share - Basic and Diluted (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Numerator:
Net income	$ 225	$ 252
Denominator for basic net income per common share:
Weighted average common shares outstanding (in shares)	12,920,000	12,804,000
Denominator for diluted net income per share:
Weighted average common shares outstanding (in shares)	12,920,000	12,804,000
Dilutive effect of stock options and restricted stock (in shares)	249,000	252,000
Diluted weighted average shares (in shares)	13,169,000	13,056,000
Earnings per common share:
Basic (in USD per share)	$ 0.02	$ 0.02
Diluted (in USD per share)	$ 0.02	$ 0.02
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Number of shares not included in the computation of dilutive income per share (in shares)	83,917	83,917
Antidilutive Effect
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Exercise price of shares not included in the computation of dilutive income per share, lower limit (in USD per share)	$ 28.15	$ 28.15
Exercise price of shares not included in the computation of dilutive income per share, upper limit (in USD per share)	$ 33.36	$ 33.36

Segment Information (Details) $ in Thousands	3 Months Ended
Segment Information (Details) $ in Thousands	Mar. 31, 2018 USD ($) segment	Mar. 31, 2017 USD ($)
Segment Reporting Information [Line Items]
Number of operating segments \| segment	1
Revenue	$ 14,718	$ 18,902
Operating costs and corporate expenses	14,368	18,559
Total other expense, net	(76)	1
Income before provision for income taxes	274	344
Corporate
Segment Reporting Information [Line Items]
Revenue	0	0
Operating costs and corporate expenses	7,408	8,374
Total other expense, net	(76)	1
Income before provision for income taxes	(7,484)	(8,373)
Rental
Segment Reporting Information [Line Items]
Revenue	11,471	11,922
Operating costs and corporate expenses	4,704	4,668
Total other expense, net	0	0
Income before provision for income taxes	6,767	7,254
Sales
Segment Reporting Information [Line Items]
Revenue	2,998	6,637
Operating costs and corporate expenses	2,191	5,423
Total other expense, net	0	0
Income before provision for income taxes	807	1,214
Service & Maintenance
Segment Reporting Information [Line Items]
Revenue	249	343
Operating costs and corporate expenses	65	94
Total other expense, net	0	0
Income before provision for income taxes	$ 184	$ 249