Quarterly Financial Data (Summary of Quarterly Financial Information) (Details) (USD $)
 3 Months Ended 12 Months Ended
Dec. 31, 2013
Sep. 30, 2013
Jun. 30, 2013
Mar. 31, 2013
Dec. 31, 2012
Sep. 30, 2012
Jun. 30, 2012
Mar. 31, 2012
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2011
Quarterly Financial Data [Line Items]                      
Total Income (Loss)                 $ (17,410,266) $ (2,623,088) $ (63,586,703)
Total Expenses                 6,133,901 5,221,100 4,616,936
Expense Waivers                 245,726 232,531 49,360
Net Expenses                 5,888,175 4,988,569 4,567,576
Net Income (Loss)                 (23,298,441) (7,611,657) (68,154,279)
United States Commodity Index Fund [Member]
                      
Quarterly Financial Data [Line Items]                      
Total Income (Loss) 308,060 25,652,345 (30,572,977) (11,934,173) (22,143,646) 27,459,791 (25,335,289) 16,846,394 (16,546,745) (3,172,750) (63,537,507)
Total Expenses 1,470,234 1,458,386 1,502,357 1,389,487 1,327,938 1,321,972 1,168,452 1,107,823 5,820,464 4,926,185 4,600,812
Expense Waivers                 0 0 36,907
Net Expenses                 5,820,464 4,926,185 4,563,905
Net Income (Loss) (1,162,174) 24,193,959 (32,075,334) (13,323,660) (23,471,584) 26,137,819 (26,503,741) 15,738,571 (22,367,209) (8,098,935) (68,101,412)
Net Income (Loss) per Share (0.10) 2.65 (3.49) (1.45) (2.90) 3.84 (3.79) 2.83      
United States Copper Index Fund [Member]
                      
Quarterly Financial Data [Line Items]                      
Total Income (Loss) 35,483 173,114 (270,337) (169,237) (81,486) 192,813 (243,242) 268,397 (230,977) [1] 136,482 [1] (49,196) [1]
Total Expenses 19,584 23,897 29,058 29,020 37,328 28,742 26,865 28,452 101,559 [1] 121,387 [1] 16,124 [1]
Expense Waivers (14,618) (19,181) (24,095) (23,895) (31,459) (23,656) (20,257) (20,992) 81,789 [1] 96,364 [1] 12,453 [1]
Net Expenses 4,966 4,716 4,963 5,125 5,869 5,086 6,608 7,460 19,770 [1] 25,023 [1] 3,671 [1]
Net Income (Loss) 30,517 168,398 (275,300) (174,362) (87,355) 187,727 (249,850) 260,937 (250,747) [1] 111,459 [1] (52,867) [1]
Net Income (Loss) per Share 0.30 1.69 (2.76) (1.74) (0.87) 1.72 (2.50) 2.61      
United States Agriculture Index Fund [Member]
                      
Quarterly Financial Data [Line Items]                      
Total Income (Loss) (82,323) 42,904 (63,796) (148,371) (174,764) 258,097 132,753 0 (251,586) [2] 216,086 [2] 0 [2]
Total Expenses 10,845 23,296 36,461 36,337 37,423 34,170 28,781 0 106,939 [2] 100,374 [2] 0 [2]
Expense Waivers (4,637) (17,041) (30,231) (29,863) (30,132) (26,019) (20,700) 0 81,772 [2] 76,851 [2] 0 [2]
Net Expenses 6,208 6,255 6,230 6,474 7,291 8,151 8,081 0 25,167 [2] 23,523 [2] 0 [2]
Net Income (Loss) (88,531) 36,649 (70,026) (154,845) (182,055) 249,946 124,672 0 (276,753) [2] 192,563 [2] 0 [2]
Net Income (Loss) per Share (0.88) 0.36 (0.70) (1.55) (1.82) 1.85 0.53 0      
United States Metals Index Fund [Member]
                      
Quarterly Financial Data [Line Items]                      
Total Income (Loss) (73,285) 217,637 (401,340) (123,970) (113,084) 339,788 (29,610) 0 (380,958) [3] 197,094 [3] 0 [3]
Total Expenses 10,099 23,760 35,404 35,676 36,406 32,701 4,047 0 104,939 [3] 73,154 [3] 0 [3]
Expense Waivers (4,987) (17,110) (30,264) (29,804) (30,139) (25,996) (3,181) 0 82,165 [3] 59,316 [3] 0 [3]
Net Expenses 5,112 6,650 5,140 5,872 6,267 6,705 866 0 22,774 [3] 13,838 [3] 0 [3]
Net Income (Loss) $ (78,397) $ 210,987 $ (406,480) $ (129,842) $ (119,351) $ 333,083 $ (30,476) $ 0 $ (403,732) [3] $ 183,256 [3] $ 0 [3]
Net Income (Loss) per Share (0.79) 1.65 (4.06) (1.30) (1.20) 2.97 (0.30) 0      
[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.