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Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified | Dec. 31, 2014 | Dec. 31, 2013
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Current Assets: |  |
Allowance for doubtful accounts | $ 507us-gaap_AllowanceForDoubtfulAccountsReceivableCurrent | $ 436us-gaap_AllowanceForDoubtfulAccountsReceivableCurrent
Allowance for inventory obsolescence | 225us-gaap_InventoryValuationReserves | 128us-gaap_InventoryValuationReserves
Assets, Noncurrent [Abstract] |  |
Accumulated depreciation, rental equipment | 106,179ngs_AccumulatedDepreciationRentalEquipment | 86,533ngs_AccumulatedDepreciationRentalEquipment
Accumulated depreciation, property and equipment | 10,830us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment | 9,692us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment
Accumulated amortization, intangibles | $ 1,257ngs_IntangibleAssetsAccumulatedAmortization | $ 1,132ngs_IntangibleAssetsAccumulatedAmortization
Stockholders' Equity Attributable to Parent [Abstract] |  |
Preferred stock, shares authorized | 5,000,000us-gaap_PreferredStockSharesAuthorized | 5,000,000us-gaap_PreferredStockSharesAuthorized
Preferred stock, shares issued | 0us-gaap_PreferredStockSharesIssued | 0us-gaap_PreferredStockSharesIssued
Preferred stock, shares outstanding | 0us-gaap_PreferredStockSharesOutstanding | 0us-gaap_PreferredStockSharesOutstanding
Common stock, par value | $ 0.01us-gaap_CommonStockParOrStatedValuePerShare | $ 0.01us-gaap_CommonStockParOrStatedValuePerShare
Common stock, shares authorized | 30,000,000us-gaap_CommonStockSharesAuthorized | 30,000,000us-gaap_CommonStockSharesAuthorized
Common stock, shares issued | 12,466,000us-gaap_CommonStockSharesIssued | 12,366,000us-gaap_CommonStockSharesIssued
Common stock, shares outstanding | 12,466,000us-gaap_CommonStockSharesOutstanding | 12,366,000us-gaap_CommonStockSharesOutstanding

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- Definition Accumulated Depreciation Rental Equipment + References No definition available. + Details
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- Definition Intangible Assets, Accumulated Amortization encompasses both finite-lived and indefinite-lived intangible assets + References No definition available. + Details
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- Definition Amount of accumulated depreciation, depletion and amortization for physical assets used in the normal conduct of business to produce goods and services. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 360 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=6391035&loc=d3e2868-110229 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.14) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 14 -Article 5 + Details
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- Definition A valuation allowance for trade and other receivables due to an Entity within one year (or the normal operating cycle, whichever is longer) that are expected to be uncollectible. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 4 -Article 5 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=35738203&loc=d3e5074-111524 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.4) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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- Definition Face amount or stated value per share of common stock. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.29) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 30 -Article 5 + Details
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- Definition The maximum number of common shares permitted to be issued by an entity's charter and bylaws. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.29) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 30 -Article 5 + Details
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- Definition Total number of common shares of an entity that have been sold or granted to shareholders (includes common shares that were issued, repurchased and remain in the treasury). These shares represent capital invested by the firm's shareholders and owners, and may be all or only a portion of the number of shares authorized. Shares issued include shares outstanding and shares held in the treasury. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.29) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 30 -Article 5 + Details
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