CONTRACTS AND AGREEMENTS - Brokerage Commission (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
United States Commodity Index Fund
Contracts and Agreements
Brokerage commissions	$ 43,611	$ 31,187	$ 111,271	$ 107,561
Brokerage commissions as a percentage of average daily net assets	0.08%	0.10%	0.08%	0.10%
United States Commodity Index Fund | Rebalancing Investments Transaction
Contracts and Agreements
Brokerage commissions			$ 102,934	$ 100,415
Brokerage commissions as a percentage of average daily net assets	92.51%	93.36%	92.51%	93.36%
United States Commodity Index Fund | Creation and Redemption Activity
Contracts and Agreements
Brokerage commissions			$ 8,337	$ 7,146
Brokerage commissions as a percentage of average daily net assets	7.49%	6.64%	7.49%	6.64%
United States Copper Index Fund
Contracts and Agreements
Brokerage commissions	$ 26,710	$ 1,672	$ 49,032	$ 4,240
Brokerage commissions as a percentage of average daily net assets	0.03%	0.04%	0.03%	0.04%
United States Copper Index Fund | Rebalancing Investments Transaction
Contracts and Agreements
Brokerage commissions			$ 34,287	$ 2,814
Brokerage commissions as a percentage of average daily net assets	69.93%	66.37%	69.93%	66.37%
United States Copper Index Fund | Creation and Redemption Activity
Contracts and Agreements
Brokerage commissions			$ 14,745	$ 1,426
Brokerage commissions as a percentage of average daily net assets	30.07%	33.63%	30.07%	33.63%