XML 44 R29.htm IDEA: XBRL DOCUMENT
v3.21.1

FINANCIAL HIGHLIGHTS - Per share performance data and other supplemental financial data (Details) - $ / shares | 3 Months Ended
--- | ---
Mar. 31, 2021 | Mar. 31, 2020
Per Share Operating Performance: |  |  |
Net asset value, beginning of year |  | $ 9.20 | $ 16.91
Total income (loss) |  | 0.44 | (4.43)
Total expenses |  | (0.03) | (0.05)
Net increase (decrease) in net asset value |  | 0.41 | (4.48)
Net asset value, end of period |  | $ 9.61 | $ 12.43
Total Return |  | 4.46% | (26.49%)
Ratios to Average Net Assets |  |  |
Total income (loss) |  | 8.46% | (28.48%)
Management fees | [1] | 0.60% | 0.60%
Total expenses excluding management fees | [1] | 0.57% | 0.73%
Net income (loss) |  | 8.18% | (28.81%)
[1] | Annualized

X
- Definition Average Net Assets [Abstract] + References No definition available. + Details
Name: | ung_AverageNetAssetsAbstract
Namespace Prefix: | ung_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Increase (Decrease) In Net Asset Value Per Unit + References No definition available. + Details
Name: | ung_IncreaseDecreaseInNetAssetValuePerUnit
Namespace Prefix: | ung_
Data Type: | num:perShareItemType
Balance Type: | na
Period Type: | duration

X
- Definition Management Incentive Fee Percentage + References No definition available. + Details
Name: | ung_ManagementIncentiveFeePercentage
Namespace Prefix: | ung_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Net asset value per unit. + References No definition available. + Details
Name: | ung_NetAssetValuePerUnit
Namespace Prefix: | ung_
Data Type: | num:perShareItemType
Balance Type: | na
Period Type: | instant

X
- Definition Percentage of Consolidated Net Income (Loss). + References No definition available. + Details
Name: | ung_PercentageOfConsolidatedNetIncomeLoss
Namespace Prefix: | ung_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Percentage of Total Revenue + References No definition available. + Details
Name: | ung_PercentageOfTotalRevenue
Namespace Prefix: | ung_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Rate Of Return On Average Asset + References No definition available. + Details
Name: | ung_RateOfReturnOnAverageAsset
Namespace Prefix: | ung_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Represents the percentage of total expenses excluding management fees. + References No definition available. + Details
Name: | ung_TotalExpensesExcludingManagementFeesPercent
Namespace Prefix: | ung_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Total Expenses, Per Unit + References No definition available. + Details
Name: | ung_TotalExpensesPerUnit
Namespace Prefix: | ung_
Data Type: | num:perShareItemType
Balance Type: | na
Period Type: | duration

X
- Definition Total Income (Loss), Per Unit + References No definition available. + Details
Name: | ung_TotalIncomeLossPerUnit
Namespace Prefix: | ung_
Data Type: | num:perShareItemType
Balance Type: | na
Period Type: | duration

X
- Definition A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period. + References No definition available. + Details
Name: | us-gaap_IncreaseDecreaseInPartnersCapitalRollForward
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration