XML 54 R39.htm IDEA: XBRL DOCUMENT
v3.19.1

Retirement of Long-Lived Assets (Details) $ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2018 USD ($) compressor | Dec. 31, 2017 USD ($) | Dec. 31, 2016 USD ($) compressor
Impaired Assets to be Disposed of by Method Other than Sale [Line Items] |  |  |
Loss on retirement of rental equipment | $ 0 | $ 0 | $ 545
Rental Compressor Unit |  |  |
Impaired Assets to be Disposed of by Method Other than Sale [Line Items] |  |  |
Estimated fair value of long-lived assets |  | 242 |
Rental Compressor Unit |  |  |
Impaired Assets to be Disposed of by Method Other than Sale [Line Items] |  |  |
Number of units retired | compressor | 13 |  |
Number of rental compressors that are not of demanded type, configuration, make or model | compressor |  |  | 63
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 |  | $ 545 |

X
- Definition Number Of Units Retired + References No definition available. + Details
Name: | ngs_NumberOfUnitsRetired
Namespace Prefix: | ngs_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- 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

X
- 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://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 360 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=109226691&loc=d3e2921-110230 + Details
Name: | us-gaap_ImpairedAssetsToBeDisposedOfByMethodOtherThanSaleAmountOfImpairmentLoss
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- 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

X
- 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://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=99377789&loc=d3e19190-110258 + Details
Name: | us-gaap_PropertyPlantAndEquipmentFairValueDisclosure
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Details
Name: | us-gaap_PropertyPlantAndEquipmentByTypeAxis=ngs_RentalCompressorUnitMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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

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