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Fair Value of Financial Instruments (Valuation of Securities Using Fair Value Hierarchy) (Details) (USD $)
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Dec. 31, 2013
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Dec. 31, 2012
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United States Commodity Index Fund [Member] | Short-Term Investments [Member]
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| Schedule of Trading Securities and Other Trading Assets [Line Items] | ||
| Securities, fair value | $ 325,142,075 | $ 435,149,105 |
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United States Commodity Index Fund [Member] | Exchange-Traded Futures Contracts [Member] | Foreign [Member]
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| Schedule of Trading Securities and Other Trading Assets [Line Items] | ||
| Securities, fair value | 6,218,462 | 2,901,485 |
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United States Commodity Index Fund [Member] | Exchange-Traded Futures Contracts [Member] | United States [Member]
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| Schedule of Trading Securities and Other Trading Assets [Line Items] | ||
| Securities, fair value | 4,571,285 | (8,122,385) |
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United States Commodity Index Fund [Member] | Fair Value, Inputs, Level 1 [Member] | Short-Term Investments [Member]
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| Schedule of Trading Securities and Other Trading Assets [Line Items] | ||
| Securities, fair value | 325,142,075 | 435,149,105 |
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United States Commodity Index Fund [Member] | Fair Value, Inputs, Level 1 [Member] | Exchange-Traded Futures Contracts [Member] | Foreign [Member]
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| Schedule of Trading Securities and Other Trading Assets [Line Items] | ||
| Securities, fair value | 6,218,462 | 2,901,485 |
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United States Commodity Index Fund [Member] | Fair Value, Inputs, Level 1 [Member] | Exchange-Traded Futures Contracts [Member] | United States [Member]
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| Schedule of Trading Securities and Other Trading Assets [Line Items] | ||
| Securities, fair value | 4,571,285 | (8,122,385) |
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United States Copper Index Fund [Member] | Short-Term Investments [Member]
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| Schedule of Trading Securities and Other Trading Assets [Line Items] | ||
| Securities, fair value | 1,599,705 | 2,149,689 |
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United States Copper Index Fund [Member] | Exchange-Traded Futures Contracts [Member] | United States [Member]
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| Schedule of Trading Securities and Other Trading Assets [Line Items] | ||
| Securities, fair value | 130,163 | 6,575 |
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United States Copper Index Fund [Member] | Fair Value, Inputs, Level 1 [Member] | Short-Term Investments [Member]
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| Schedule of Trading Securities and Other Trading Assets [Line Items] | ||
| Securities, fair value | 1,599,705 | 2,149,689 |
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United States Copper Index Fund [Member] | Fair Value, Inputs, Level 1 [Member] | Exchange-Traded Futures Contracts [Member] | United States [Member]
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| Schedule of Trading Securities and Other Trading Assets [Line Items] | ||
| Securities, fair value | 130,163 | 6,575 |
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United States Agriculture Index Fund [Member] | Short-Term Investments [Member]
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| Schedule of Trading Securities and Other Trading Assets [Line Items] | ||
| Securities, fair value | 1,499,678 | 2,199,688 |
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United States Agriculture Index Fund [Member] | Exchange-Traded Futures Contracts [Member] | Foreign [Member]
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| Schedule of Trading Securities and Other Trading Assets [Line Items] | ||
| Securities, fair value | 2,216 | (31,470) |
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United States Agriculture Index Fund [Member] | Exchange-Traded Futures Contracts [Member] | United States [Member]
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| Schedule of Trading Securities and Other Trading Assets [Line Items] | ||
| Securities, fair value | (46,749) | (87,685) |
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United States Agriculture Index Fund [Member] | Fair Value, Inputs, Level 1 [Member] | Short-Term Investments [Member]
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| Schedule of Trading Securities and Other Trading Assets [Line Items] | ||
| Securities, fair value | 1,499,678 | 2,199,688 |
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United States Agriculture Index Fund [Member] | Fair Value, Inputs, Level 1 [Member] | Exchange-Traded Futures Contracts [Member] | Foreign [Member]
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| Schedule of Trading Securities and Other Trading Assets [Line Items] | ||
| Securities, fair value | 2,216 | (31,470) |
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United States Agriculture Index Fund [Member] | Fair Value, Inputs, Level 1 [Member] | Exchange-Traded Futures Contracts [Member] | United States [Member]
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| Schedule of Trading Securities and Other Trading Assets [Line Items] | ||
| Securities, fair value | (46,749) | (87,685) |
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United States Metals Index Fund [Member] | Short-Term Investments [Member]
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| Schedule of Trading Securities and Other Trading Assets [Line Items] | ||
| Securities, fair value | 1,199,914 | 2,349,792 |
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United States Metals Index Fund [Member] | Exchange-Traded Futures Contracts [Member] | Foreign [Member]
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| Schedule of Trading Securities and Other Trading Assets [Line Items] | ||
| Securities, fair value | (12,610) | 77,393 |
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United States Metals Index Fund [Member] | Exchange-Traded Futures Contracts [Member] | United States [Member]
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| Schedule of Trading Securities and Other Trading Assets [Line Items] | ||
| Securities, fair value | (33,683) | (31,335) |
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United States Metals Index Fund [Member] | Fair Value, Inputs, Level 1 [Member] | Short-Term Investments [Member]
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| Schedule of Trading Securities and Other Trading Assets [Line Items] | ||
| Securities, fair value | 1,199,914 | 2,349,792 |
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United States Metals Index Fund [Member] | Fair Value, Inputs, Level 1 [Member] | Exchange-Traded Futures Contracts [Member] | Foreign [Member]
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| Schedule of Trading Securities and Other Trading Assets [Line Items] | ||
| Securities, fair value | (12,610) | 77,393 |
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United States Metals Index Fund [Member] | Fair Value, Inputs, Level 1 [Member] | Exchange-Traded Futures Contracts [Member] | United States [Member]
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| Schedule of Trading Securities and Other Trading Assets [Line Items] | ||
| Securities, fair value | $ (33,683) | $ (31,335) |