Name:	ngs_LineOfCreditFacilityCurrentBorrowingCapacityComponentPercentOfEligibleAccountsReceivableOwingByNonInvestmentGradeDebtors
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Line Of Credit Facility Current Borrowing Capacity Component Percentage Of Eligible Compressors For Extension Of Credit

No definition available.

Name:	ngs_LineOfCreditFacilityCurrentBorrowingCapacityComponentPercentageOfEligibleCompressorsForExtensionOfCredit
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Line Of Credit Facility Current Borrowing Capacity Component Percentage Of Eligible Inventory

No definition available.

Name:	ngs_LineOfCreditFacilityCurrentBorrowingCapacityComponentPercentageOfEligibleInventory
Namespace Prefix:	ngs_
Data Type:	dtr-types:percentItemType
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Line Of Credit Facility Current Borrowing Capacity Component Percentage Of Eligible Value At Cost Excluding Any Cost For Capitalized Interest Or Other Non Cash Capitalized Costs

No definition available.

Name:	ngs_LineOfCreditFacilityCurrentBorrowingCapacityComponentPercentageOfEligibleValueAtCostExcludingAnyCostForCapitalizedInterestOrOtherNonCashCapitalizedCosts
Namespace Prefix:	ngs_
Data Type:	dtr-types:percentItemType
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Line Of Credit Facility Current Borrowing Capacity Net Liquidation Value Of Percentage Of Eligible Compressors For Extension Of Credit

No definition available.

Name:	ngs_LineOfCreditFacilityCurrentBorrowingCapacityNetLiquidationValueOfPercentageOfEligibleCompressorsForExtensionOfCredit
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Line Of Credit Facility, Default Trigger, Certain Defaults Of Other Company Indebtedness, Amount

No definition available.

Name:	ngs_LineOfCreditFacilityDefaultTriggerCertainDefaultsOfOtherCompanyIndebtednessAmount
Namespace Prefix:	ngs_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Line Of Credit Facility, Default Trigger, Rendering Of Certain Judgments, Amount

No definition available.

Name:	ngs_LineOfCreditFacilityDefaultTriggerRenderingOfCertainJudgmentsAmount
Namespace Prefix:	ngs_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Line Of Credit Facility Fixed Charge Coverage Ratio

No definition available.

Name:	ngs_LineOfCreditFacilityFixedChargeCoverageRatio
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Data Type:	xbrli:pureItemType
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Line of Credit Facility, Maximum Leverage Ratio Allowed

No definition available.

Name:	ngs_LineOfCreditFacilityLeverageRatio
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Balance Type:	na
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Line Of Credit Facility Non Exceeding Cap Of Component Capacity

No definition available.

Name:	ngs_LineOfCreditFacilityNonExceedingCapOfComponentCapacity
Namespace Prefix:	ngs_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Line Of Credit Facility, Potential Increase In Borrowing Capacity

No definition available.

Name:	ngs_LineOfCreditFacilityPotentialIncreaseInBorrowingCapacity
Namespace Prefix:	ngs_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Line Of Credit Facility, Potential Maximum Borrowing Capacity

No definition available.

Name:	ngs_LineOfCreditFacilityPotentialMaximumBorrowingCapacity
Namespace Prefix:	ngs_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Line Of Credit Facility Term For Depreciation

No definition available.

Name:	ngs_LineOfCreditFacilityTermForDepreciation
Namespace Prefix:	ngs_
Data Type:	xbrli:durationItemType
Balance Type:	na
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Percentage points added to the reference rate to compute the variable rate on the debt instrument.

No definition available.

Name:	us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
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Data Type:	dtr-types:percentItemType
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Period Type:	duration

Period of time between issuance and maturity of debt instrument, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

No definition available.

Name:	us-gaap_DebtInstrumentTerm
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
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Period Type:	duration

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI https://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-URI https://asc.fasb.org/extlink&oid=126897435&loc=d3e534808-122878

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(16))
-URI https://asc.fasb.org/extlink&oid=126734703&loc=d3e572229-122910

Name:	us-gaap_LineOfCredit
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Amount of current borrowing capacity under the credit facility considering any current restrictions on the amount that could be borrowed (for example, borrowings may be limited by the amount of current assets), but without considering any amounts currently outstanding under the facility.

Name:	us-gaap_LineOfCreditFacilityCurrentBorrowingCapacity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

No definition available.

Name:	us-gaap_LineOfCreditFacilityLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

Name:	us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

Name:	us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

The fee, expressed as a percentage of the line of credit facility, for available but unused credit capacity under the credit facility.

No definition available.

Name:	us-gaap_LineOfCreditFacilityUnusedCapacityCommitmentFeePercentage
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

Weighted average interest rate of long-term debt outstanding calculated over time.

No definition available.

Name:	us-gaap_LongTermDebtWeightedAverageInterestRateOverTime
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

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Name:	srt_StatementScenarioAxis=srt_ScenarioForecastMember
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Name:	us-gaap_SubsequentEventTypeAxis=us-gaap_SubsequentEventMember
Namespace Prefix:
Data Type:	na
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Name:	us-gaap_DebtInstrumentAxis=ngs_NewCreditAgreementMember
Namespace Prefix:
Data Type:	na
Balance Type:
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Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_LineOfCreditMember
Namespace Prefix:
Data Type:	na
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Name:	srt_RangeAxis=srt_MaximumMember
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Name:	us-gaap_VariableRateAxis=ngs_FederalFundRateMember
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Data Type:	na
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