Name:	ngs_LineOfCreditFacilityCurrentBorrowingCapacityComponentPercentOfEligibleAccountsReceivableOwingByNonInvestmentGradeDebtors
Namespace Prefix:	ngs_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

Line Of Credit Facility, Current Borrowing Capacity Component Percentage Of Eligible Accounts Receivable Owing By Investment Grade Debtors

No definition available.

Name:	ngs_LineOfCreditFacilityCurrentBorrowingCapacityComponentPercentageOfEligibleAccountsReceivableOwingByInvestmentGradeDebtors
Namespace Prefix:	ngs_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

Line Of Credit Facility, Current Borrowing Capacity, Component, Percentage Of Eligible Compressors For Extension Of Credit

No definition available.

Name:	ngs_LineOfCreditFacilityCurrentBorrowingCapacityComponentPercentageOfEligibleCompressorsForExtensionOfCredit
Namespace Prefix:	ngs_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

Line Of Credit Facility, Current Borrowing Capacity Component Percentage Of Eligible Inventory

No definition available.

Name:	ngs_LineOfCreditFacilityCurrentBorrowingCapacityComponentPercentageOfEligibleInventory
Namespace Prefix:	ngs_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

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:	num:percentItemType
Balance Type:	na
Period Type:	instant

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
Namespace Prefix:	ngs_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

No definition available.

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

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
Namespace Prefix:	ngs_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	duration

Line Of Credit Facility Leverage Ratio

No definition available.

Name:	ngs_LineOfCreditFacilityLeverageRatio
Namespace Prefix:	ngs_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	duration

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

No definition available.

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

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
Period Type:	duration

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

No definition available.

Name:	us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
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
Balance Type:	na
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 http://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 http://asc.fasb.org/extlink&oid=120398452&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 http://asc.fasb.org/extlink&oid=120400017&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

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

Detail information of subsequent event by type. User is expected to use existing line items from elsewhere in the taxonomy as the primary line items for this disclosure, which is further associated with dimension and member elements pertaining to a subsequent event.

No definition available.

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

Name:	us-gaap_CreditFacilityAxis=us-gaap_RevolvingCreditFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_SubsequentEventTypeAxis=us-gaap_SubsequentEventMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	srt_RangeAxis=srt_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_VariableRateAxis=ngs_FederalFundRateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_VariableRateAxis=ngs_EurodollarRateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	srt_RangeAxis=srt_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: