XML 44 R27.htm IDEA: XBRL DOCUMENT v3.8.0.1

CONTRACTS AND AGREEMENTS (Brokerage Commission) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Commissions accrued to brokers	$ 1,728,440	$ 2,000,888	$ 2,371,433
Percentage of commissions accrued	0.35%	0.37%	0.39%
Rebalancing Investments Transaction [Member]
Commissions accrued to brokers	$ 1,420,519	$ 1,872,019	$ 2,089,974
Percentage of commissions accrued	82.19%	93.56%	88.13%
Creation And Redemption Activity [Member]
Commissions accrued to brokers	$ 307,921	$ 128,869	$ 281,459
Percentage of commissions accrued	17.81%	6.44%	11.87%

X

- Definition

Percentage of Average Daily Net Assets

+ References

No definition available.

+ Details

Name:	ung_PercentageOfAverageDailyNetAssets
Namespace Prefix:	ung_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

X

- Definition

The amount of expense during the period for floor brokerage fees paid to other broker-dealers to execute trades on their behalf, stock exchange fees, order flow fees, and clearance fees.

+ References

No definition available.

+ Details

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

X

- Details

Name:	us-gaap_StatementClassOfStockAxis=ung_RebalancingInvestmentsTransactionMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_StatementClassOfStockAxis=ung_TradesNecessitatedByCreationAndRedemptionActivityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: