Statements of Changes in Partners' Capital - USD ($)	United States Commodity Index Fund [Member]	United States Copper Index Fund [Member]	United States Commodity Index Funds Trust [Member]	Sponsor [Member] United States Commodity Index Fund [Member]	Sponsor [Member] United States Copper Index Fund [Member]	Sponsor [Member] United States Commodity Index Funds Trust [Member]	Shareholders [Member] United States Commodity Index Fund [Member]	Shareholders [Member] United States Copper Index Fund [Member]	Shareholders [Member] United States Commodity Index Funds Trust [Member]
Net income (loss)	$ 2,873,099	$ (1,206,325)	$ 1,649,964
Net asset value, beginning of period (in dollars per share) at Dec. 31, 2017	$ 42.48	$ 21.05
Net asset value, end of period (in dollars per share) at Mar. 31, 2018	$ 42.72	$ 19.30
Balances, Beginning at Dec. 31, 2018	$ 463,042,508	$ 11,504,895	474,547,403	$ 0	$ 0		$ 463,042,508	$ 11,504,895	$ 474,547,403
Additions		5,451,099	5,451,099		0	$ 0		5,451,099	5,451,099
Redemptions	(40,713,896)	(1,651,189)	(42,365,085)	0	0	0	(40,713,896)	(1,651,189)	(42,365,085)
Net income (loss)	16,243,487	1,219,154	17,462,641	0	0	0	16,243,487	1,219,154	17,462,641
Balances, Ending at Mar. 31, 2019	$ 438,572,099	$ 16,523,959	$ 455,096,058	$ 0	$ 0	$ 0	$ 438,572,099	$ 16,523,959	$ 455,096,058
Shares Outstanding, Beginning at Dec. 31, 2018	12,350,000	700,000	13,050,000	0	0	0	12,350,000	700,000	13,050,000
Additions	0	300,000	300,000	0	0	0	0	300,000	300,000
Redemptions	(1,050,000)	(100,000)	(1,150,000)	0	0	0	(1,050,000)	(100,000)	(1,150,000)
Shares Outstanding, Ending at Mar. 31, 2019	11,300,000	900,000	12,200,000	0	0	0	11,300,000	900,000	12,200,000
Net asset value, beginning of period (in dollars per share) at Dec. 31, 2018	$ 37.49	$ 16.44
Net asset value, end of period (in dollars per share) at Mar. 31, 2019	$ 38.81	$ 18.36