Statements of Cash Flows (USD $)
 12 Months Ended
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2011
Cash Flows from Operating Activities:      
Net income (loss) $ (23,298,441) $ (7,611,657) $ (68,154,279)
Adjustments to reconcile net income (loss) to net cash used in operating activities:      
(Increase) decrease in commodity futures trading account - cash and cash equivalents 40,897,436 2,471,491 (56,145,173)
Unrealized (gain) loss on futures contracts (16,116,506) (17,751,283) 30,456,022
(Increase) decrease in receivable from Sponsor (13,195) (220,078) 38,944
(Increase) decrease in interest receivable (812) (379) 353
Increase in other assets (3,468) (2,128) (2,558)
Increase (decrease) in management fees payable 8,611 69,497 263,456
Increase (decrease) in professional fees payable 45,749 272,063 207,229
Increase (decrease) in brokerage commissions payable 0 (3,380) 21,110
Increase (decrease) in directors' fees payable 4,320 (7,548) 19,335
Increase (decrease) in other liabilities (1) 0 153
Net cash provided by (used in) operating activities 1,523,693 (22,783,402) (93,295,408)
Cash Flows from Financing Activities:      
Addition of shares 123,611,309 178,807,041 472,181,512
Redemption of shares (82,000,053) (31,585,138) (153,724,157)
Net cash provided by (used in) financing activities 41,611,256 147,221,903 318,457,355
Net Increase (Decrease) in Cash and Cash Equivalents 43,134,949 124,438,501 225,161,947
Cash and Cash Equivalents, beginning of year 437,046,560 312,608,059 87,446,112
Cash and Cash Equivalents, end of year 480,181,509 437,046,560 312,608,059
United States Commodity Index Fund [Member]
      
Cash Flows from Operating Activities:      
Net income (loss) (22,367,209) (8,098,935) (68,101,412)
Adjustments to reconcile net income (loss) to net cash used in operating activities:      
(Increase) decrease in commodity futures trading account - cash and cash equivalents 40,003,074 3,653,943 (55,747,624)
Unrealized (gain) loss on futures contracts (16,010,647) (17,755,792) 30,394,009
(Increase) decrease in receivable from Sponsor 0 0 51,397
(Increase) decrease in interest receivable (787) (329) 360
Increase in other assets (3,388) (2,099) (2,558)
Increase (decrease) in management fees payable 9,261 66,737 261,470
Increase (decrease) in professional fees payable 31,367 43,160 194,304
Increase (decrease) in brokerage commissions payable 0 (3,380) 21,110
Increase (decrease) in directors' fees payable 4,297 (7,706) 19,303
Increase (decrease) in other liabilities (1) 0 153
Net cash provided by (used in) operating activities 1,665,967 (22,104,401) (92,909,488)
Cash Flows from Financing Activities:      
Addition of shares 122,521,532 168,769,146 469,681,512
Redemption of shares (80,864,053) (26,356,666) (153,723,138)
Net cash provided by (used in) financing activities 41,657,479 142,412,480 315,958,374
Net Increase (Decrease) in Cash and Cash Equivalents 43,323,446 120,308,079 223,048,886
Cash and Cash Equivalents, beginning of year 430,800,077 310,491,998 87,443,112
Cash and Cash Equivalents, end of year 474,123,523 430,800,077 310,491,998
United States Copper Index Fund [Member]
      
Cash Flows from Operating Activities:      
Net income (loss) (250,747) [1] 111,459 [1] (52,867) [1]
Adjustments to reconcile net income (loss) to net cash used in operating activities:      
(Increase) decrease in commodity futures trading account - cash and cash equivalents 306,569 [1] (34,980) [1] (397,549) [1]
Unrealized (gain) loss on futures contracts (123,588) [1] (68,588) [1] 62,013 [1]
(Increase) decrease in receivable from Sponsor 14,575 [1] (83,911) [1] (12,453) [1]
(Increase) decrease in interest receivable (7) [1] (11) [1] (7) [1]
Increase in other assets (7) [1] (29) [1] 0 [1]
Increase (decrease) in management fees payable (164) [1] (593) [1] 1,986 [1]
Increase (decrease) in professional fees payable (14,965) [1] 87,268 [1] 12,925 [1]
Increase (decrease) in directors' fees payable 8 [1] 12 [1] 32 [1]
Net cash provided by (used in) operating activities (68,326) [1] 10,627 [1] (385,920) [1]
Cash Flows from Financing Activities:      
Addition of shares 0 [1] 1,224,883 [1] 2,500,000 [1]
Redemption of shares 0 [1] (1,240,510) [1] (1,019) [1]
Net cash provided by (used in) financing activities 0 [1] (15,627) [1] 2,498,981 [1]
Net Increase (Decrease) in Cash and Cash Equivalents (68,326) [1] (5,000) [1] 2,113,061 [1]
Cash and Cash Equivalents, beginning of year 2,109,061 [1] 2,114,061 [1] 1,000 [1]
Cash and Cash Equivalents, end of year 2,040,735 [1] 2,109,061 [1] 2,114,061 [1]
United States Agriculture Index Fund [Member]
      
Cash Flows from Operating Activities:      
Net income (loss) (276,753) [2] 192,563 [2] 0 [2]
Adjustments to reconcile net income (loss) to net cash used in operating activities:      
(Increase) decrease in commodity futures trading account - cash and cash equivalents 449,326 [2] (679,407) [2] 0 [2]
Unrealized (gain) loss on futures contracts (74,622) [2] 119,155 [2] 0 [2]
(Increase) decrease in receivable from Sponsor (4,921) [2] (76,851) [2] 0 [2]
(Increase) decrease in interest receivable (14) [2] (32) [2] 0 [2]
Increase in other assets (36) [2] 0 [2] 0 [2]
Increase (decrease) in management fees payable (202) [2] 1,772 [2] 0 [2]
Increase (decrease) in professional fees payable 5,320 [2] 80,030 [2] 0 [2]
Increase (decrease) in directors' fees payable 9 [2] 79 [2] 0 [2]
Net cash provided by (used in) operating activities 98,107 [2] (362,691) [2] 0 [2]
Cash Flows from Financing Activities:      
Addition of shares 0 [2] 5,085,695 [2] 0 [2]
Redemption of shares 0 [2] (2,723,566) [2] 0 [2]
Net cash provided by (used in) financing activities 0 [2] 2,362,129 [2] 0 [2]
Net Increase (Decrease) in Cash and Cash Equivalents 98,107 [2] 1,999,438 [2] 0 [2]
Cash and Cash Equivalents, beginning of year 2,000,438 [2] 1,000 [2] 1,000 [2]
Cash and Cash Equivalents, end of year 2,098,545 [2] 2,000,438 [2] 1,000 [2]
United States Metals Index Fund [Member]
      
Cash Flows from Operating Activities:      
Net income (loss) (403,732) [3] 183,256 [3] 0 [3]
Adjustments to reconcile net income (loss) to net cash used in operating activities:      
(Increase) decrease in commodity futures trading account - cash and cash equivalents 138,467 [3] (468,065) [3] 0 [3]
Unrealized (gain) loss on futures contracts 92,351 [3] (46,058) [3] 0 [3]
(Increase) decrease in receivable from Sponsor (22,849) [3] (59,316) [3] 0 [3]
(Increase) decrease in interest receivable (4) [3] (7) [3] 0 [3]
Increase in other assets (37) [3] 0 [3] 0 [3]
Increase (decrease) in management fees payable (284) [3] 1,581 [3] 0 [3]
Increase (decrease) in professional fees payable 24,027 [3] 61,605 [3] 0 [3]
Increase (decrease) in directors' fees payable 6 [3] 67 [3] 0 [3]
Net cash provided by (used in) operating activities (172,055) [3] (326,937) [3] 0 [3]
Cash Flows from Financing Activities:      
Addition of shares 1,089,777 [3] 3,727,317 [3] 0 [3]
Redemption of shares (1,136,000) [3] (1,264,396) [3] 0 [3]
Net cash provided by (used in) financing activities (46,223) [3] 2,462,921 [3] 0 [3]
Net Increase (Decrease) in Cash and Cash Equivalents (218,278) [3] 2,135,984 [3] 0 [3]
Cash and Cash Equivalents, beginning of year 2,136,984 [3] 1,000 [3] 1,000 [3]
Cash and Cash Equivalents, end of year $ 1,918,706 [3] $ 2,136,984 [3] $ 1,000 [3]
[1] The commencement of operations of the United States Copper Index Fund was November 15, 2011.
[2] The commencement of operations of the United States Agriculture Index Fund was April 13, 2012.
[3] The commencement of operations of the United States Metals Index Fund was June 19, 2012.