XML 50 R33.htm IDEA: XBRL DOCUMENT v3.8.0.1

FAIR VALUE OF FINANCIAL INSTRUMENTS (Fair Value of Derivative Instruments) (Details) - USD ($)	Dec. 31, 2017	Dec. 31, 2016
Commodity Contracts [Member] | Futures - Commodity Contracts [Member] | Assets [Member]
Fair Value of Financial Instruments [Line Items]
Derivatives not Accounted for as Hedging Instruments	$ 55,721,680	$ 37,435,507

X

- Definition

Fair Value of Financial Instruments [Line Items]

+ References

No definition available.

+ Details

Name:	ung_FairValueOfFinancialInstrumentsLineItems
Namespace Prefix:	ung_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Fair value as of the balance sheet date of derivative instrument not designated as hedging instrument and classified as an asset.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4B
-Subparagraph (c)(2)
-URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5624163-113959

+ Details

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

X

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=us-gaap_CommodityContractMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_FutureMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_BalanceSheetLocationAxis=us-gaap_AssetsTotalMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: