FAIR VALUE OF FINANCIAL INSTRUMENTS (Valuation of Securities Using Fair Value Hierarchy) (Details) - USD ($)	Mar. 31, 2019	Dec. 31, 2018
United States Commodity Index Fund [Member] | Short-Term Investments [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Securities, fair value	$ 439,767,236	$ 436,426,995
United States Commodity Index Fund [Member] | Exchange-Traded Futures Contracts [Member] | Foreign [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Securities, fair value	9,829,353	(1,866,820)
United States Commodity Index Fund [Member] | Exchange-Traded Futures Contracts [Member] | United States [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Securities, fair value	(6,167,234)	(12,621,164)
United States Commodity Index Fund [Member] | Fair Value, Inputs, Level 1 [Member] | Short-Term Investments [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Securities, fair value	439,767,236	436,426,995
United States Commodity Index Fund [Member] | Fair Value, Inputs, Level 1 [Member] | Exchange-Traded Futures Contracts [Member] | Foreign [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Securities, fair value	9,829,353	(1,866,820)
United States Commodity Index Fund [Member] | Fair Value, Inputs, Level 1 [Member] | Exchange-Traded Futures Contracts [Member] | United States [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Securities, fair value	(6,167,234)	(12,621,164)
United States Commodity Index Fund [Member] | Fair Value, Inputs, Level 2 [Member] | Short-Term Investments [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Securities, fair value	0	0
United States Commodity Index Fund [Member] | Fair Value, Inputs, Level 2 [Member] | Exchange-Traded Futures Contracts [Member] | Foreign [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Securities, fair value	0	0
United States Commodity Index Fund [Member] | Fair Value, Inputs, Level 2 [Member] | Exchange-Traded Futures Contracts [Member] | United States [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Securities, fair value	0	0
United States Commodity Index Fund [Member] | Fair Value, Inputs, Level 3 [Member] | Short-Term Investments [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Securities, fair value	0	0
United States Commodity Index Fund [Member] | Fair Value, Inputs, Level 3 [Member] | Exchange-Traded Futures Contracts [Member] | Foreign [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Securities, fair value	0	0
United States Commodity Index Fund [Member] | Fair Value, Inputs, Level 3 [Member] | Exchange-Traded Futures Contracts [Member] | United States [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Securities, fair value	0	0
United States Copper Index Fund [Member] | Short-Term Investments [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Securities, fair value	15,330,079	9,657,426
United States Copper Index Fund [Member] | Exchange-Traded Futures Contracts [Member] | United States [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Securities, fair value	532,625	(903,475)
United States Copper Index Fund [Member] | Fair Value, Inputs, Level 1 [Member] | Short-Term Investments [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Securities, fair value	15,330,079	9,657,426
United States Copper Index Fund [Member] | Fair Value, Inputs, Level 1 [Member] | Exchange-Traded Futures Contracts [Member] | United States [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Securities, fair value	532,625	(903,475)
United States Copper Index Fund [Member] | Fair Value, Inputs, Level 2 [Member] | Short-Term Investments [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Securities, fair value	0	0
United States Copper Index Fund [Member] | Fair Value, Inputs, Level 2 [Member] | Exchange-Traded Futures Contracts [Member] | United States [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Securities, fair value	0	0
United States Copper Index Fund [Member] | Fair Value, Inputs, Level 3 [Member] | Short-Term Investments [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Securities, fair value	0	0
United States Copper Index Fund [Member] | Fair Value, Inputs, Level 3 [Member] | Exchange-Traded Futures Contracts [Member] | United States [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Securities, fair value	$ 0	$ 0