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SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details)	9 Months Ended
	Sep. 30, 2019 USD ($) $ / item
Significant Accounting Policies [Line Items]
Fee paid by Authorized Purchasers for each order placed to create one or more Creation Baskets or to redeem one or more baskets	1,000
Unrecognized Tax Benefits, Income Tax Penalties and Interest Expense | $	$ 0
Redemption Baskets [Member]
Significant Accounting Policies [Line Items]
Number of units per basket	100,000

X

- Definition

Fee Paid Per Order

+ References

No definition available.

+ Details

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Namespace Prefix:	ung_
Data Type:	srt-types:perUnitItemType
Balance Type:	na
Period Type:	instant

X

- Definition

Number of unit per basket.

+ References

No definition available.

+ Details

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Namespace Prefix:	ung_
Data Type:	srt-types:perUnitItemType
Balance Type:	na
Period Type:	instant

X

- Definition

Significant Accounting Policies [Line Items]

+ References

No definition available.

+ Details

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Namespace Prefix:	ung_
Data Type:	xbrli:stringItemType
Balance Type:	na
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X

- Definition

Amount of expense for interest on an underpayment of income taxes and penalties related to a tax position claimed or expected to be claimed in the tax return.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 15
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32718-109319

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

X

- Details

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Namespace Prefix:
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Balance Type:
Period Type: