FINANCIAL HIGHLIGHTS - Per Unit Performance Data and Other Supplemental Financial Data (Details)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
United States Copper Index Fund
Percentage of average daily net assets paid monthly, waiver expense	0.64%	0.43%	0.39%
Percentage of expenses exceeded	0.15%
Effective January 1, 2016 | United States Copper Index Fund
Percentage of average daily net assets paid monthly, waiver expense	0.65%
Effective January 1, 2016 | United States Commodity Index Fund
Percentage of average daily net assets paid monthly, waiver expense	0.80%