Condensed Statements of Financial Condition - USD ($)		Sep. 30, 2021	Dec. 31, 2020
Assets
Cash and cash equivalents		$ 467,105,470
United States Commodity Index Fund
Assets
Cash and cash equivalents		218,105,747	$ 103,318,538
Equity in trading accounts:
Cash and cash equivalents		11,711,481	554,470
Unrealized gain (loss) on open commodity futures contracts		5,966,412	7,293,344
Dividends receivable		4,544	2,379
Interest receivable		6	0
Prepaid insurance	[1]	15,535	5,212
Prepaid registration fees		16,596	0
Total Assets		235,820,321	111,173,943
Liabilities and Capital
Management fees payable (Note 4)		152,976	72,934
Professional fees payable		158,686	312,461
Brokerage commissions payable		3,955	3,955
Directors' fees payable	[1]	4,250	1,525
Total Liabilities		319,867	390,875
Commitments and Contingencies (Notes 4, 5 & 6)
Capital
Sponsor		0	0
Shareholders		235,500,454	110,783,068
Total Capital		235,500,454	110,783,068
Total Liabilities and Capital		$ 235,820,321	$ 111,173,943
Shares outstanding		5,750,000	3,400,000
Net asset value per share		$ 40.96	$ 32.58
Market value per share		$ 40.89	$ 32.67
United States Copper Index Fund
Assets
Cash and cash equivalents		$ 248,999,723	$ 62,333,565
Equity in trading accounts:
Cash and cash equivalents		15,094,341	0
Unrealized gain (loss) on open commodity futures contracts		(3,576,834)	4,296,063
Receivable from Sponsor (Note 4)		0	58,202
Dividends receivable		5,371	1,315
Interest receivable		3	6
Prepaid insurance	[1]	15,840	228
Prepaid registration fees		59,841	0
ETF transaction fees receivable		350	0
Total Assets		260,598,635	66,689,379
Liabilities and Capital
Payable due to Broker		0	1,428,240
Payable for shares redeemed		22,526,184	0
Management fees payable (Note 4)		147,393	31,116
Professional fees payable		146,408	61,244
Directors' fees payable	[1]	6,806	5,075
Total Liabilities		22,826,791	1,525,675
Commitments and Contingencies (Notes 4, 5 & 6)
Capital
Sponsor		0	0
Shareholders		237,771,844	65,163,704
Total Capital		237,771,844	65,163,704
Total Liabilities and Capital		$ 260,598,635	$ 66,689,379
Shares outstanding		9,500,000	3,000,000
Net asset value per share		$ 25.03	$ 21.72
Market value per share		$ 25.05	$ 21.73
United States Commodity Index Funds Trust
Assets
Cash and cash equivalents		$ 467,105,470	$ 165,652,103
Equity in trading accounts:
Cash and cash equivalents		26,805,822	554,470
Unrealized gain (loss) on open commodity futures contracts		2,389,578	11,589,407
Receivable from Sponsor (Note 4)		0	58,202
Dividends receivable		9,915	3,694
Interest receivable		9	6
Prepaid insurance	[1]	31,375	5,440
Prepaid registration fees		76,437	0
ETF transaction fees receivable		350	0
Total Assets		496,418,956	177,863,322
Liabilities and Capital
Payable due to Broker		0	1,428,240
Payable for shares redeemed		22,526,184	0
Management fees payable (Note 4)		300,369	104,050
Professional fees payable		305,094	373,705
Brokerage commissions payable		3,955	3,955
Directors' fees payable	[1]	11,056	6,600
Total Liabilities		23,146,658	1,916,550
Commitments and Contingencies (Notes 4, 5 & 6)
Capital
Sponsor		0	0
Shareholders		473,272,298	175,946,772
Total Capital		473,272,298	175,946,772
Total Liabilities and Capital		$ 496,418,956	$ 177,863,322
Shares outstanding		15,250,000	6,400,000

[1] Certain prior year amounts have been reclassified for consistency with the current presentation.