CONTRACTS AND AGREEMENTS (Brokerage Commission) (Details) - USD ($)	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
United States Commodity Index Fund [Member]
Long-Duration Contracts, Assumptions by Product and Guarantee [Line Items]
Brokerage commissions	$ 176,921	$ 169,522
Brokerage commissions as a percentage of average daily net assets	0.16%	0.13%
United States Commodity Index Fund [Member] | Rebalancing Investments Transaction [Member]
Long-Duration Contracts, Assumptions by Product and Guarantee [Line Items]
Brokerage commissions	$ 173,345	$ 164,193
Brokerage commissions as a percentage of average daily net assets	97.98%	96.86%
United States Commodity Index Fund [Member] | Creation and Redemption Activity [Member]
Long-Duration Contracts, Assumptions by Product and Guarantee [Line Items]
Brokerage commissions	$ 3,576	$ 5,329
Brokerage commissions as a percentage of average daily net assets	2.02%	3.14%
United States Copper Index Fund [Member]
Long-Duration Contracts, Assumptions by Product and Guarantee [Line Items]
Brokerage commissions	$ 1,509	$ 2,198
Brokerage commissions as a percentage of average daily net assets	0.05%	0.06%
United States Copper Index Fund [Member] | Rebalancing Investments Transaction [Member]
Long-Duration Contracts, Assumptions by Product and Guarantee [Line Items]
Brokerage commissions	$ 1,286	$ 1,953
Brokerage commissions as a percentage of average daily net assets	85.22%	88.85%
United States Copper Index Fund [Member] | Creation and Redemption Activity [Member]
Long-Duration Contracts, Assumptions by Product and Guarantee [Line Items]
Brokerage commissions	$ 223	$ 245
Brokerage commissions as a percentage of average daily net assets	14.78%	11.15%