Basis of Presentation and Summary of Significant Accounting Policies	9 Months Ended
Sep. 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 unaudited 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 September 30, 2011 and the results of our operations for the three and nine months ended September 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 accounting principles generally accepted 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 nine months ended September 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 September 2011, the FASB issued ASU No. 2011-08, “Intangibles - Goodwill and Other (ASC 350): Testing Goodwill for Impairment,” which specifies that an entity has the option to first assess qualitative factors to determine whether it is more likely than not that the fair value of a reporting unit is less than its carrying amount as a basis for determining whether it is necessary to perform the two-step goodwill impairment test. An entity is not required to calculate the fair value of a reporting unit unless the entity determines that it is more likely than not that its fair value is less than its carrying amount. ASU No. 2011-08 is effective for fiscal years, and interim periods within those years, beginning after December 15, 2011. We do not expect the adoption of ASU No. 2011-08 will have a material impact on our consolidated financial condition and results of operations.

Basis of Presentation and Summary of Significant Accounting Policies

These notes apply to the unaudited 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 September 30, 2011 and the results of our operations for the three and nine months ended September 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 accounting principles generally accepted 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 nine months ended September 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 September 2011, the FASB issued ASU No. 2011-08, “Intangibles - Goodwill and Other (ASC 350): Testing Goodwill for Impairment,” which specifies that an entity has the option to first assess qualitative factors to determine whether it is more likely than not that the fair value of a reporting unit is less than its carrying amount as a basis for determining whether it is necessary to perform the two-step goodwill impairment test. An entity is not required to calculate the fair value of a reporting unit unless the entity determines that it is more likely than not that its fair value is less than its carrying amount. ASU No. 2011-08 is effective for fiscal years, and interim periods within those years, beginning after December 15, 2011. We do not expect the adoption of ASU No. 2011-08 will have a material impact on our consolidated financial condition and results of operations.