FINANCIAL HIGHLIGHTS (Per Unit Performance Data and Other Supplemental Financial Data) (Details) - $ / shares		3 Months Ended
		Mar. 31, 2019	Mar. 31, 2018
United States Commodity Index Fund [Member]
Per Share Operating Performance:
Net asset value, beginning of period (in dollars per share)		$ 37.49	$ 42.48
Total income (loss)		1.43	0.35
Total expenses		(0.11)	(0.11)
Net increase (decrease) in net asset value		1.32	0.24
Net asset value, end of period (in dollars per share)		$ 38.81	$ 42.72
Total Return		3.52%	0.56%
Ratios to Average Net Assets
Total income (loss)		3.79%	0.81%
Management fees	[1],[2]	0.80%	0.80%
Total expenses excluding management fees	[1]	0.32%	0.27%
Expenses waived	[1],[2]	0.00%	0.00%
Net expenses excluding management fees	[1]	0.32%	0.27%
Net income (loss)		3.51%	0.55%
United States Copper Index Fund [Member]
Per Share Operating Performance:
Net asset value, beginning of period (in dollars per share)		$ 16.44	$ 21.05
Total income (loss)		1.95	(1.71)
Total expenses		(0.03)	(0.04)
Net increase (decrease) in net asset value		1.92	(1.75)
Net asset value, end of period (in dollars per share)		$ 18.36	$ 19.30
Total Return		11.68%	(8.31%)
Ratios to Average Net Assets
Total income (loss)		10.64%	(8.46%)
Management fees	[1],[3]	0.65%	0.65%
Total expenses excluding management fees	[1]	0.91%	0.39%
Expenses waived	[1],[3],[4]	(0.76%)	(0.24%)
Net expenses excluding management fees	[1]	0.15%	0.15%
Net income (loss)		10.45%	(8.66%)

[1] Annualized

[2] Effective January 1, 2016, USCF permanently lowered the management fee to 0.80% (80 basis points) per annum of average daily total net assets for USCI.

[3] Effective January 1, 2016, USCF permanently lowered the management fee to 0.65% (65 basis points) per annum of average daily total net assets for CPER.

[4] USCF paid certain expenses on a discretionary basis typically borne by CPER where expenses exceeded 0.15% (15 basis points) of CPER’s NAV, on an annualized basis. USCF has no obligation to continue such payments into subsequent periods.