Statements of Financial Condition (USD $)
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2013
United States Commodity Index Fund [Member]
Dec. 31, 2012
United States Commodity Index Fund [Member]
Dec. 31, 2013
United States Copper Index Fund [Member]
Dec. 31, 2012
United States Copper Index Fund [Member]
Dec. 31, 2013
United States Agriculture Index Fund [Member]
Dec. 31, 2012
United States Agriculture Index Fund [Member]
Dec. 31, 2013
United States Metals Index Fund [Member]
Dec. 31, 2012
United States Metals Index Fund [Member]
Assets                    
Cash and cash equivalents (Notes 2 and 6) $ 480,181,509 $ 437,046,560 $ 474,123,523 $ 430,800,077 $ 2,040,735 [1] $ 2,109,061 [1] $ 2,098,545 [2] $ 2,000,438 [2] $ 1,918,706 $ 2,136,984
Equity in Newedge trading accounts:                    
Cash and cash equivalents 21,002,192 61,899,628 20,316,553 60,319,627 125,960 432,529 230,081 679,407 329,598 468,065
Unrealized gain (loss) on open commodity futures contracts 10,829,084 (5,287,422) 10,789,747 (5,220,900) 130,163 6,575 (44,533) (119,155) (46,293) 46,058
Receivable for shares sold 8,491,911 2,922,886 8,491,911 2,922,886            
Receivable from Sponsor (Note 4) 245,726 232,531     81,789 96,364 81,772 76,851 82,165 59,316
Interest receivable 1,343 531 1,261 474 25 18 46 32 11 7
Other assets 8,154 4,686 8,045 4,657 36 29 36 0 37 0
Total assets 520,759,919 496,819,400 513,731,040 488,826,821 2,378,708 2,644,576 2,365,947 2,637,573 2,284,224 2,710,430
Liabilities and Capital                    
Management fees payable (Note 4) 407,590 398,979 403,494 394,233 1,229 1,393 1,570 1,772 1,297 1,581
Professional fees payable 599,873 554,124 343,663 312,296 85,228 100,193 85,350 80,030 85,632 61,605
Brokerage commissions payable 22,815 22,815 22,815 22,815            
Directors' fees payable 16,107 11,787 15,894 11,597 52 44 88 79 73 67
Other liabilities 152 153 152 153            
Total liabilities 1,046,537 987,858 786,018 741,094 86,509 101,630 87,008 81,881 87,002 63,253
Commitments and Contingencies (Notes 4, 5 and 6)                              
Capital                    
Sponsor 0 0 0 0 0 0 0 0 0 0
Shareholders 519,713,382 495,831,542 512,945,022 488,085,727 2,292,199 2,542,946 2,278,939 2,555,692 2,197,222 2,647,177
Total Capital 519,713,382 495,831,542 512,945,022 488,085,727 2,292,199 2,542,946 2,278,939 2,555,692 2,197,222 2,647,177
Total liabilities and capital $ 520,759,919 $ 496,819,400 $ 513,731,040 $ 488,826,821 $ 2,378,708 $ 2,644,576 $ 2,365,947 $ 2,637,573 $ 2,284,224 $ 2,710,430
Shares outstanding 9,450,000 8,650,000 9,150,000 8,350,000 100,000 100,000 100,000 100,000 100,000 100,000
Net asset value per share     $ 56.06 $ 58.45 $ 22.92 $ 25.43 $ 22.79 $ 25.56 [3] $ 21.97 $ 26.47 [4]
Market value per share     $ 56.08 $ 58.63 $ 22.90 $ 25.01 $ 22.35 $ 25.59 $ 21.02 $ 31.07
[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 USAG was April 13, 2012.
[4] The commencement of operations of USMI was June 19, 2012.