FAIR VALUE OF FINANCIAL INSTRUMENTS - Effect of Derivative Instruments on Condensed Statements of Operations of Usci, Cper, Usag and Usmi (Details) - USD ($)	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
FAIR VALUE OF FINANCIAL INSTRUMENTS
Realized Gain (Loss) on Derivatives Recognized in Income	$ (30,279,328)	$ (56,209,907)	$ 24,220,537
Change in Unrealized Gain (Loss) on Derivatives Recognized in Income	17,876,577	(23,145,242)	5,699,448
United States Commodity Index Fund
FAIR VALUE OF FINANCIAL INSTRUMENTS
Realized Gain (Loss) on Derivatives Recognized in Income	(29,144,478)	(54,710,680)	22,989,718
Change in Unrealized Gain (Loss) on Derivatives Recognized in Income	16,626,852	(21,360,954)	4,817,510
United States Commodity Index Fund \| Commodity Contracts \| Futures \| Realized gain (loss) on closed positions
FAIR VALUE OF FINANCIAL INSTRUMENTS
Realized Gain (Loss) on Derivatives Recognized in Income	(29,144,478)	(54,710,680)	22,989,718
United States Commodity Index Fund \| Commodity Contracts \| Futures \| Change in unrealized gain (loss) on open positions
FAIR VALUE OF FINANCIAL INSTRUMENTS
Change in Unrealized Gain (Loss) on Derivatives Recognized in Income	16,626,852	(21,360,954)	4,817,510
United States Copper Index Fund
FAIR VALUE OF FINANCIAL INSTRUMENTS
Realized Gain (Loss) on Derivatives Recognized in Income	(1,134,850)	(1,318,188)	1,468,825
Change in Unrealized Gain (Loss) on Derivatives Recognized in Income	1,249,725	(1,785,413)	793,363
United States Copper Index Fund \| Commodity Contracts \| Futures \| Realized gain (loss) on closed positions
FAIR VALUE OF FINANCIAL INSTRUMENTS
Realized Gain (Loss) on Derivatives Recognized in Income	(1,134,850)	(1,318,188)	1,468,825
United States Copper Index Fund \| Commodity Contracts \| Futures \| Change in unrealized gain (loss) on open positions
FAIR VALUE OF FINANCIAL INSTRUMENTS
Change in Unrealized Gain (Loss) on Derivatives Recognized in Income	$ 1,249,725	$ (1,785,413)	$ 793,363

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The net realized gain (loss) on investments sold during the period, not including gains (losses) on securities separately or otherwise categorized as trading, available-for-sale, or held-to-maturity, which, for cash flow reporting, is a component of proceeds from investing activities.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3602-108585

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The net change in the difference between the fair value and the carrying value, or in the comparative fair values, of open derivatives, commodity, or energy contracts, held at each balance sheet date, that was included in earnings for the period.

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