FAIR VALUE OF FINANCIAL INSTRUMENTS - Fair Value of Derivative Instrument held by Usci, Cper, Usag and Usmi (Details) - Not designated as Hedging Instrument - Commodity Contracts - Futures - Assets. - USD ($)	Sep. 30, 2021	Dec. 31, 2020
United States Commodity Index Fund
FAIR VALUE OF FINANCIAL INSTRUMENTS
Derivative Asset	$ 5,966,412	$ 7,293,344
United States Copper Index Fund
FAIR VALUE OF FINANCIAL INSTRUMENTS
Derivative Asset	$ 3,576,834	$ (4,296,063)