Aggregate Amount of Power Retired From Fleet

No definition available.

Name:	ngs_AggregateAmountofPowerRetiredFromFleet
Namespace Prefix:	ngs_
Data Type:	num:powerItemType
Balance Type:	na
Period Type:	instant

- Definition

Number of Units Designated as Impaired Assets to be Disposed of by Method Other than Sale

+ References

No definition available.

+ Details

Name:	ngs_NumberofUnitsDesignatedasImpairedAssetstobeDisposedofbyMethodOtherthanSale
Namespace Prefix:	ngs_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Loss recognized as a result of the initial and subsequent write-down of a long-lived asset's carrying amount to fair value.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=64862545&loc=d3e2921-110230

+ Details

Name:	us-gaap_ImpairedAssetsToBeDisposedOfByMethodOtherThanSaleAmountOfImpairmentLoss
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

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.

+ References

No definition available.

+ Details

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

- Definition

Fair value portion of physical assets used in the normal conduct of business to produce goods and services and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, and furniture and fixtures.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19190-110258

+ Details

Name:	us-gaap_PropertyPlantAndEquipmentFairValueDisclosure
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

Name:	us-gaap_ImpairedAssetsToBeDisposedOfByMethodOtherThanSaleByTypeAxis=ngs_RentalCompressorUnitMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_IncomeStatementLocationAxis=ngs_LossonRetirementofRentalEquipmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Retirement of Long-Lived Assets (Details)	3 Months Ended			9 Months Ended
Retirement of Long-Lived Assets (Details)	Sep. 30, 2016 USD ($)	Sep. 30, 2015 USD ($)	Jun. 30, 2015 USD ($) rental_compressor hp	Sep. 30, 2016 USD ($)	Sep. 30, 2015 USD ($)
Impaired Assets to be Disposed of by Method Other than Sale [Line Items]
Amount of rental compressor horsepower \| hp			32,259
Loss on retirement of rental equipment	$ 0	$ (3,000)		$ 0	$ 4,370,000
Rental Compressor Unit
Impaired Assets to be Disposed of by Method Other than Sale [Line Items]
Number of rental compressors to be retired \| rental_compressor			258
Estimated fair value of long-lived assets			$ 967,000
Rental Compressor Unit \| Loss on Retirement of Rental Equipment
Impaired Assets to be Disposed of by Method Other than Sale [Line Items]
Loss on retirement of rental equipment			$ 4,400,000