Basis of Presentation and Summary of Significant Accounting Policies	6 Months Ended
Jun. 30, 2011
Basis of Presentation and Summary of Significant Accounting Policies [Abstract]
Basis of Presentation and Significant Accounting Policies [Text Block]	Basis of Presentation and Summary of Significant Accounting Policies These notes apply to the condensed financial statements of Natural Gas Services Group, Inc. (the "Company", “NGSG”, "Natural Gas Services Group", "we" or "our") (a Colorado corporation). We were formed on December 17, 1998 for the purposes of combining the operations of certain manufacturing, service and leasing entities. The accompanying unaudited condensed financial statements present the condensed results of our Company taken from our books and records. In our opinion, such information includes all adjustments, consisting of only normal recurring adjustments, which are necessary to make our financial position at June 30, 2011 and the results of our operations for the three and six months ended June 30, 2010 and 2011 not misleading. As permitted by the rules and regulations of the Securities and Exchange Commission (SEC) the accompanying condensed 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, 2010 on file with the SEC. In our opinion, the condensed 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 six months ended June 30, 2011 are not necessarily indicative of the results of operations to be expected for the full fiscal year ending December 31, 2011. Revenue recognition Revenue from the sales of custom and fabricated compressors, and flare systems is recognized upon shipment of the equipment to customers or when all conditions have been met or title is transferred to the customer. Exchange and rebuild compressor revenue is recognized when both the replacement compressor has been delivered and the rebuild assessment has been completed. Revenue from compressor services is recognized upon providing services to the customer. Maintenance agreement revenue is recognized as services are rendered. Rental revenue is recognized over the terms of the respective rental agreements based upon the classification of the rental agreement. Deferred income represents payments received before a product is shipped. Revenue from the sale of rental units is included in sales revenue when equipment is shipped or title is transferred to the customer. Fair Value of Financial Instruments Our financial instruments consist principally of cash and cash equivalents, accounts receivable, accounts payable 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 current fair values because of their nature and respective relatively short maturity dates or durations. Recently Issued Accounting Pronouncements In January 2010, the FASB (Financial Accounting Standards Board) issued authoritative guidance intended to improve disclosures about fair value measurements. The guidance requires entities to disclose significant transfers in and out of fair value hierarchy levels and the reasons for the transfers and to present information about purchases, sales, issuances and settlements separately in the reconciliation of fair value measurements using significant unobservable inputs (Level 3). Additionally, the guidance clarifies that a reporting entity should provide fair value measurements for each class of assets and liabilities and disclose the inputs and valuation techniques used for fair value measurements using significant other observable inputs (Level 2) and significant unobservable inputs (Level 3). This guidance was effective for us on January 1, 2010 except for the disclosures about purchases, sales, issuances and settlements in the Level 3 reconciliation; this portion became effective on January 1, 2011. As this guidance provides only disclosure requirements, the adoption of this standard did not impact our results of operations, cash flows or financial position. In March 2010, the FASB issued authoritative guidance intended to clarify the scope exception related to embedded credit derivative features related to the transfer of credit risk in the form of subordination of one financial instrument to another. The guidance addresses how to determine which embedded credit derivative features, including those in collateralized debt obligations and synthetic collateralized debt obligations, are considered to be embedded derivatives that should not be analyzed under Accounting Standards Codification Topic 815, “Derivatives and Hedging” Subtopic 15-25 for potential bifurcation and separate accounting. This guidance is effective for each reporting entity at the beginning of its fiscal quarter beginning after September 15, 2010. We do not have any embedded credit derivative features with respect to our financial instruments; therefore, this standard did not have any impact on our financial statements.

Basis of Presentation and Summary of Significant Accounting Policies

These notes apply to the condensed financial statements of Natural Gas Services Group, Inc. (the "Company", “NGSG”, "Natural Gas Services Group", "we" or "our") (a Colorado corporation). We were formed on December 17, 1998 for the purposes of combining the operations of certain manufacturing, service and leasing entities.

The accompanying unaudited condensed financial statements present the condensed results of our Company taken from our books and records. In our opinion, such information includes all adjustments, consisting of only normal recurring adjustments, which are necessary to make our financial position at June 30, 2011 and the results of our operations for the three and six months ended June 30, 2010 and 2011 not misleading. As permitted by the rules and regulations of the Securities and Exchange Commission (SEC) the accompanying condensed 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, 2010 on file with the SEC. In our opinion, the condensed 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 six months ended June 30, 2011 are not necessarily indicative of the results of operations to be expected for the full fiscal year ending December 31, 2011.

Revenue recognition

Revenue from the sales of custom and fabricated compressors, and flare systems is recognized upon shipment of the equipment to customers or when all conditions have been met or title is transferred to the customer. Exchange and rebuild compressor revenue is recognized when both the replacement compressor has been delivered and the rebuild assessment has been completed. Revenue from compressor services is recognized upon providing services to the customer. Maintenance agreement revenue is recognized as services are rendered. Rental revenue is recognized over the terms of the respective rental agreements based upon the classification of the rental agreement. Deferred income represents payments received before a product is shipped. Revenue from the sale of rental units is included in sales revenue when equipment is shipped or title is transferred to the customer.

Fair Value of Financial Instruments

Our financial instruments consist principally of cash and cash equivalents, accounts receivable, accounts payable 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 current fair values because of their nature and respective relatively short maturity dates or durations.

Recently Issued Accounting Pronouncements

In January 2010, the FASB (Financial Accounting Standards Board) issued authoritative guidance intended to improve disclosures about fair value measurements. The guidance requires entities to disclose significant transfers in and out of fair value hierarchy levels and the reasons for the transfers and to present information about purchases, sales, issuances and settlements separately in the reconciliation of fair value measurements using significant unobservable inputs (Level 3). Additionally, the guidance clarifies that a reporting entity should provide fair value measurements for each class of assets and liabilities and disclose the inputs and valuation techniques used for fair value measurements using significant other observable inputs (Level 2) and significant unobservable inputs (Level 3). This guidance was effective for us on January 1, 2010 except for the disclosures about purchases, sales, issuances and settlements in the Level 3 reconciliation; this portion became effective on January 1, 2011. As this guidance provides only disclosure requirements, the adoption of this standard did not impact our results of operations, cash flows or financial position.

In March 2010, the FASB issued authoritative guidance intended to clarify the scope exception related to embedded credit derivative features related to the transfer of credit risk in the form of subordination of one financial instrument to another. The guidance addresses how to determine which embedded credit derivative features, including those in collateralized debt obligations and synthetic collateralized debt obligations, are considered to be embedded derivatives that should not be analyzed under Accounting Standards Codification Topic 815, “Derivatives and Hedging” Subtopic 15-25 for potential bifurcation and separate accounting. This guidance is effective for each reporting entity at the beginning of its fiscal quarter beginning after September 15, 2010. We do not have any embedded credit derivative features with respect to our financial instruments; therefore, this standard did not have any impact on our financial statements.