CONTRACTS AND AGREEMENTS - Brokerage Commission (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Contracts and Agreements
Brokerage commissions	$ 460,079	$ 546,563	$ 534,994
United States Commodity Index Fund
Contracts and Agreements
Brokerage commissions	$ 453,997	$ 539,884	$ 527,610
Brokerage commissions as a percentage of average daily net assets	0.13%	0.09%	0.10%
United States Commodity Index Fund | Rebalancing Investments Transaction
Contracts and Agreements
Brokerage commissions	$ 429,823	$ 508,021	$ 505,199
Brokerage commissions as a percentage of average daily net assets	94.68%	94.10%	95.75%
United States Commodity Index Fund | Creation and Redemption Activity
Contracts and Agreements
Brokerage commissions	$ 24,174	$ 31,863	$ 22,411
Brokerage commissions as a percentage of average daily net assets	5.32%	5.90%	4.25%
United States Copper Index Fund
Contracts and Agreements
Brokerage commissions	$ 6,082	$ 5,181	$ 5,461
Brokerage commissions as a percentage of average daily net assets	0.06%	0.04%	0.05%
United States Copper Index Fund | Rebalancing Investments Transaction
Contracts and Agreements
Brokerage commissions	$ 5,353	$ 4,205	$ 4,390
Brokerage commissions as a percentage of average daily net assets	88.01%	81.16%	80.39%
United States Copper Index Fund | Creation and Redemption Activity
Contracts and Agreements
Brokerage commissions	$ 729	$ 976	$ 1,071
Brokerage commissions as a percentage of average daily net assets	11.99%	18.84%	19.61%