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Investments (Effect Of Derivative Instruments On Statements Of Operations) (Detail) (USD $)
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3 Months Ended | |
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Mar. 31, 2013
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Mar. 31, 2012
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| Derivative Instruments, Gain (Loss) [Line Items] | ||
| Realized Gain or (Loss) on Derivatives Recognized in Income | $ (230,349,276) | $ (166,787,901) |
| Change in Unrealized Appreciation or Depreciation on Derivatives Recognized in Income | 86,306,510 | 4,840,424 |
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Commodity Contracts [Member] | Net Realized Gain (Loss) On Futures Contracts, Swap And/ Or Forward Agreements/ Changes In Unrealized Appreciation/ Depreciation On Futures Contracts, Swap And/ Or Forward Agreements [Member] | ProShares UltraShort DJ-UBS Commodity [Member]
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| Derivative Instruments, Gain (Loss) [Line Items] | ||
| Realized Gain or (Loss) on Derivatives Recognized in Income | 308,498 | 74,310 |
| Change in Unrealized Appreciation or Depreciation on Derivatives Recognized in Income | (241,421) | (361,088) |
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Commodity Contracts [Member] | Net Realized Gain (Loss) On Futures Contracts, Swap And/ Or Forward Agreements/ Changes In Unrealized Appreciation/ Depreciation On Futures Contracts, Swap And/ Or Forward Agreements [Member] | ProShares UltraShort DJ-UBS Crude Oil [Member]
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| Derivative Instruments, Gain (Loss) [Line Items] | ||
| Realized Gain or (Loss) on Derivatives Recognized in Income | (6,125,158) | (3,831,611) |
| Change in Unrealized Appreciation or Depreciation on Derivatives Recognized in Income | (1,500,109) | (901,690) |
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Commodity Contracts [Member] | Net Realized Gain (Loss) On Futures Contracts, Swap And/ Or Forward Agreements/ Changes In Unrealized Appreciation/ Depreciation On Futures Contracts, Swap And/ Or Forward Agreements [Member] | ProShares UltraShort DJ-UBS Natural Gas [Member]
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| Derivative Instruments, Gain (Loss) [Line Items] | ||
| Realized Gain or (Loss) on Derivatives Recognized in Income | (1,773,421) | 4,437,111 |
| Change in Unrealized Appreciation or Depreciation on Derivatives Recognized in Income | (3,905,888) | 5,930,960 |
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Commodity Contracts [Member] | Net Realized Gain (Loss) On Futures Contracts, Swap And/ Or Forward Agreements/ Changes In Unrealized Appreciation/ Depreciation On Futures Contracts, Swap And/ Or Forward Agreements [Member] | ProShares UltraShort Gold [Member]
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| Derivative Instruments, Gain (Loss) [Line Items] | ||
| Realized Gain or (Loss) on Derivatives Recognized in Income | 12,883,467 | (1,545,985) |
| Change in Unrealized Appreciation or Depreciation on Derivatives Recognized in Income | (6,992,788) | (33,068,073) |
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Commodity Contracts [Member] | Net Realized Gain (Loss) On Futures Contracts, Swap And/ Or Forward Agreements/ Changes In Unrealized Appreciation/ Depreciation On Futures Contracts, Swap And/ Or Forward Agreements [Member] | ProShares UltraShort Silver [Member]
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| Derivative Instruments, Gain (Loss) [Line Items] | ||
| Realized Gain or (Loss) on Derivatives Recognized in Income | 29,204,512 | (35,684,414) |
| Change in Unrealized Appreciation or Depreciation on Derivatives Recognized in Income | (19,064,897) | (34,342,752) |
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Commodity Contracts [Member] | Net Realized Gain (Loss) On Futures Contracts, Swap And/ Or Forward Agreements/ Changes In Unrealized Appreciation/ Depreciation On Futures Contracts, Swap And/ Or Forward Agreements [Member] | ProShares Ultra DJ-UBS Commodity [Member]
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| Derivative Instruments, Gain (Loss) [Line Items] | ||
| Realized Gain or (Loss) on Derivatives Recognized in Income | (508,897) | (322,448) |
| Change in Unrealized Appreciation or Depreciation on Derivatives Recognized in Income | 421,315 | 421,325 |
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Commodity Contracts [Member] | Net Realized Gain (Loss) On Futures Contracts, Swap And/ Or Forward Agreements/ Changes In Unrealized Appreciation/ Depreciation On Futures Contracts, Swap And/ Or Forward Agreements [Member] | ProShares Ultra DJ-UBS Crude Oil [Member]
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| Derivative Instruments, Gain (Loss) [Line Items] | ||
| Realized Gain or (Loss) on Derivatives Recognized in Income | 66,564,325 | 15,544,135 |
| Change in Unrealized Appreciation or Depreciation on Derivatives Recognized in Income | (28,737,943) | 9,089,628 |
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Commodity Contracts [Member] | Net Realized Gain (Loss) On Futures Contracts, Swap And/ Or Forward Agreements/ Changes In Unrealized Appreciation/ Depreciation On Futures Contracts, Swap And/ Or Forward Agreements [Member] | ProShares Ultra DJ-UBS Natural Gas [Member]
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| Derivative Instruments, Gain (Loss) [Line Items] | ||
| Realized Gain or (Loss) on Derivatives Recognized in Income | 5,748,194 | (5,158,571) |
| Change in Unrealized Appreciation or Depreciation on Derivatives Recognized in Income | 17,861,568 | (15,543,310) |
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Commodity Contracts [Member] | Net Realized Gain (Loss) On Futures Contracts, Swap And/ Or Forward Agreements/ Changes In Unrealized Appreciation/ Depreciation On Futures Contracts, Swap And/ Or Forward Agreements [Member] | ProShares Ultra Gold [Member]
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| Derivative Instruments, Gain (Loss) [Line Items] | ||
| Realized Gain or (Loss) on Derivatives Recognized in Income | (50,415,205) | (29,858,796) |
| Change in Unrealized Appreciation or Depreciation on Derivatives Recognized in Income | 24,891,118 | 76,461,894 |
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Commodity Contracts [Member] | Net Realized Gain (Loss) On Futures Contracts, Swap And/ Or Forward Agreements/ Changes In Unrealized Appreciation/ Depreciation On Futures Contracts, Swap And/ Or Forward Agreements [Member] | ProShares Ultra Silver [Member]
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| Derivative Instruments, Gain (Loss) [Line Items] | ||
| Realized Gain or (Loss) on Derivatives Recognized in Income | (215,688,548) | 8,106,450 |
| Change in Unrealized Appreciation or Depreciation on Derivatives Recognized in Income | 137,646,238 | 132,908,783 |
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Foreign Exchange Contracts [Member] | Net Realized Gain (Loss) On Foreign Currency Forward Contracts/ Changes In Unrealized Appreciation/ Depreciation On Foreign Currency Forward Contracts [Member] | ProShares Short Euro [Member]
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| Derivative Instruments, Gain (Loss) [Line Items] | ||
| Realized Gain or (Loss) on Derivatives Recognized in Income | (8,000) | |
| Change in Unrealized Appreciation or Depreciation on Derivatives Recognized in Income | 116,769 | |
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Foreign Exchange Contracts [Member] | Net Realized Gain (Loss) On Foreign Currency Forward Contracts/ Changes In Unrealized Appreciation/ Depreciation On Foreign Currency Forward Contracts [Member] | ProShares UltraShort Australian Dollar [Member]
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| Derivative Instruments, Gain (Loss) [Line Items] | ||
| Realized Gain or (Loss) on Derivatives Recognized in Income | 112,030 | |
| Change in Unrealized Appreciation or Depreciation on Derivatives Recognized in Income | (195,160) | |
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Foreign Exchange Contracts [Member] | Net Realized Gain (Loss) On Foreign Currency Forward Contracts/ Changes In Unrealized Appreciation/ Depreciation On Foreign Currency Forward Contracts [Member] | ProShares UltraShort Euro [Member]
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| Derivative Instruments, Gain (Loss) [Line Items] | ||
| Realized Gain or (Loss) on Derivatives Recognized in Income | (2,949,680) | 38,812,588 |
| Change in Unrealized Appreciation or Depreciation on Derivatives Recognized in Income | 26,813,021 | (98,488,552) |
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Foreign Exchange Contracts [Member] | Net Realized Gain (Loss) On Foreign Currency Forward Contracts/ Changes In Unrealized Appreciation/ Depreciation On Foreign Currency Forward Contracts [Member] | ProShares UltraShort Yen [Member]
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| Derivative Instruments, Gain (Loss) [Line Items] | ||
| Realized Gain or (Loss) on Derivatives Recognized in Income | 96,886,297 | 20,853,004 |
| Change in Unrealized Appreciation or Depreciation on Derivatives Recognized in Income | (35,381,549) | 17,433,639 |
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Foreign Exchange Contracts [Member] | Net Realized Gain (Loss) On Foreign Currency Forward Contracts/ Changes In Unrealized Appreciation/ Depreciation On Foreign Currency Forward Contracts [Member] | ProShares Ultra Australian Dollar [Member]
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| Derivative Instruments, Gain (Loss) [Line Items] | ||
| Realized Gain or (Loss) on Derivatives Recognized in Income | (149,275) | |
| Change in Unrealized Appreciation or Depreciation on Derivatives Recognized in Income | 223,960 | |
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Foreign Exchange Contracts [Member] | Net Realized Gain (Loss) On Foreign Currency Forward Contracts/ Changes In Unrealized Appreciation/ Depreciation On Foreign Currency Forward Contracts [Member] | ProShares Ultra Euro [Member]
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| Derivative Instruments, Gain (Loss) [Line Items] | ||
| Realized Gain or (Loss) on Derivatives Recognized in Income | (65,362) | (249,576) |
| Change in Unrealized Appreciation or Depreciation on Derivatives Recognized in Income | (221,155) | 811,782 |
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Foreign Exchange Contracts [Member] | Net Realized Gain (Loss) On Foreign Currency Forward Contracts/ Changes In Unrealized Appreciation/ Depreciation On Foreign Currency Forward Contracts [Member] | ProShares Ultra Yen [Member]
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| Derivative Instruments, Gain (Loss) [Line Items] | ||
| Realized Gain or (Loss) on Derivatives Recognized in Income | (1,217,971) | (425,209) |
| Change in Unrealized Appreciation or Depreciation on Derivatives Recognized in Income | 423,734 | (328,692) |
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VIX Futures Contracts [Member] | Net Realized Gain (Loss) On Futures Contracts/ Changes In Unrealized Appreciation/ Depreciation On Futures Contracts [Member] | ProShares VIX Short-Term Futures ETF [Member]
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| Derivative Instruments, Gain (Loss) [Line Items] | ||
| Realized Gain or (Loss) on Derivatives Recognized in Income | (55,408,949) | (42,732,137) |
| Change in Unrealized Appreciation or Depreciation on Derivatives Recognized in Income | (8,124,641) | (17,345,947) |
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VIX Futures Contracts [Member] | Net Realized Gain (Loss) On Futures Contracts/ Changes In Unrealized Appreciation/ Depreciation On Futures Contracts [Member] | ProShares VIX Mid-Term Futures ETF [Member]
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| Derivative Instruments, Gain (Loss) [Line Items] | ||
| Realized Gain or (Loss) on Derivatives Recognized in Income | (10,260,171) | (22,417,600) |
| Change in Unrealized Appreciation or Depreciation on Derivatives Recognized in Income | (406,019) | (5,041,600) |
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VIX Futures Contracts [Member] | Net Realized Gain (Loss) On Futures Contracts/ Changes In Unrealized Appreciation/ Depreciation On Futures Contracts [Member] | ProShares Ultra VIX Short-Term Futures ETF [Member]
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| Derivative Instruments, Gain (Loss) [Line Items] | ||
| Realized Gain or (Loss) on Derivatives Recognized in Income | (122,690,073) | (119,246,992) |
| Change in Unrealized Appreciation or Depreciation on Derivatives Recognized in Income | (21,095,534) | (33,611,433) |
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VIX Futures Contracts [Member] | Net Realized Gain (Loss) On Futures Contracts/ Changes In Unrealized Appreciation/ Depreciation On Futures Contracts [Member] | ProShares Short VIX Short-Term Futures ETF [Member]
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| Derivative Instruments, Gain (Loss) [Line Items] | ||
| Realized Gain or (Loss) on Derivatives Recognized in Income | 25,204,111 | 6,857,840 |
| Change in Unrealized Appreciation or Depreciation on Derivatives Recognized in Income | $ 3,775,891 | $ 815,550 |