v2.4.0.6
Investments (Fair Value of Derivative Instruments) (Detail) (USD $)
Mar. 31, 2013
Dec. 31, 2012
Derivative Instruments, Gain (Loss) [Line Items]    
Derivative asset not designated as hedging instrument, Unrealized Appreciation $ 70,881,000 [1] $ 124,994,834 [1]
Derivative liability not designated as hedging instrument, Unrealized Depreciation 57,067,666 [1] 197,488,010 [1]
Commodity Contracts [Member] | Payable On Open Futures Contracts, Unrealized Depreciation On Swap And/ Or Forward Agreements [Member] | ProShares UltraShort DJ-UBS Commodity [Member]
    
Derivative Instruments, Gain (Loss) [Line Items]    
Derivative liability not designated as hedging instrument, Unrealized Depreciation 92,919  
Commodity Contracts [Member] | Payable On Open Futures Contracts, Unrealized Depreciation On Swap And/ Or Forward Agreements [Member] | ProShares UltraShort DJ-UBS Crude Oil [Member]
    
Derivative Instruments, Gain (Loss) [Line Items]    
Derivative liability not designated as hedging instrument, Unrealized Depreciation 11,368,414 9,636,781 [1]
Commodity Contracts [Member] | Payable On Open Futures Contracts, Unrealized Depreciation On Swap And/ Or Forward Agreements [Member] | ProShares UltraShort DJ-UBS Natural Gas [Member]
    
Derivative Instruments, Gain (Loss) [Line Items]    
Derivative liability not designated as hedging instrument, Unrealized Depreciation 3,496,753 [1]  
Commodity Contracts [Member] | Payable On Open Futures Contracts, Unrealized Depreciation On Swap And/ Or Forward Agreements [Member] | ProShares UltraShort Gold [Member]
    
Derivative Instruments, Gain (Loss) [Line Items]    
Derivative liability not designated as hedging instrument, Unrealized Depreciation 3,247,692 [1]  
Commodity Contracts [Member] | Payable On Open Futures Contracts, Unrealized Depreciation On Swap And/ Or Forward Agreements [Member] | ProShares UltraShort Silver [Member]
    
Derivative Instruments, Gain (Loss) [Line Items]    
Derivative liability not designated as hedging instrument, Unrealized Depreciation 11,313  
Commodity Contracts [Member] | Payable On Open Futures Contracts, Unrealized Depreciation On Swap And/ Or Forward Agreements [Member] | ProShares Ultra Silver [Member]
    
Derivative Instruments, Gain (Loss) [Line Items]    
Derivative liability not designated as hedging instrument, Unrealized Depreciation 8,134,488 [1] 145,780,726 [1]
Commodity Contracts [Member] | Payable On Open Futures Contracts, Unrealized Depreciation On Swap And/ Or Forward Agreements [Member] | ProShares Ultra DJ-UBS Commodity [Member]
    
Derivative Instruments, Gain (Loss) [Line Items]    
Derivative liability not designated as hedging instrument, Unrealized Depreciation   306,268
Commodity Contracts [Member] | Payable On Open Futures Contracts, Unrealized Depreciation On Swap And/ Or Forward Agreements [Member] | ProShares Ultra DJ-UBS Natural Gas [Member]
    
Derivative Instruments, Gain (Loss) [Line Items]    
Derivative liability not designated as hedging instrument, Unrealized Depreciation   3,816,950 [1]
Commodity Contracts [Member] | Payable On Open Futures Contracts, Unrealized Depreciation On Swap And/ Or Forward Agreements [Member] | ProShares Ultra Gold [Member]
    
Derivative Instruments, Gain (Loss) [Line Items]    
Derivative liability not designated as hedging instrument, Unrealized Depreciation   15,667,298 [1]
Commodity Contracts [Member] | Receivables On Open Futures Contracts, Unrealized Appreciation On Swap And/ Or Forwards Agreements [Member] | ProShares UltraShort DJ-UBS Commodity [Member]
    
Derivative Instruments, Gain (Loss) [Line Items]    
Derivative asset not designated as hedging instrument, Unrealized Appreciation   148,502
Commodity Contracts [Member] | Receivables On Open Futures Contracts, Unrealized Appreciation On Swap And/ Or Forwards Agreements [Member] | ProShares UltraShort DJ-UBS Crude Oil [Member]
    
Derivative Instruments, Gain (Loss) [Line Items]    
Derivative asset not designated as hedging instrument, Unrealized Appreciation 231,524 [1]  
Commodity Contracts [Member] | Receivables On Open Futures Contracts, Unrealized Appreciation On Swap And/ Or Forwards Agreements [Member] | ProShares UltraShort DJ-UBS Natural Gas [Member]
    
Derivative Instruments, Gain (Loss) [Line Items]    
Derivative asset not designated as hedging instrument, Unrealized Appreciation   409,135 [1]
Commodity Contracts [Member] | Receivables On Open Futures Contracts, Unrealized Appreciation On Swap And/ Or Forwards Agreements [Member] | ProShares UltraShort Gold [Member]
    
Derivative Instruments, Gain (Loss) [Line Items]    
Derivative asset not designated as hedging instrument, Unrealized Appreciation   3,745,096 [1]
Commodity Contracts [Member] | Receivables On Open Futures Contracts, Unrealized Appreciation On Swap And/ Or Forwards Agreements [Member] | ProShares UltraShort Silver [Member]
    
Derivative Instruments, Gain (Loss) [Line Items]    
Derivative asset not designated as hedging instrument, Unrealized Appreciation 294,121 [1] 19,347,705 [1]
Commodity Contracts [Member] | Receivables On Open Futures Contracts, Unrealized Appreciation On Swap And/ Or Forwards Agreements [Member] | ProShares Ultra DJ-UBS Commodity [Member]
    
Derivative Instruments, Gain (Loss) [Line Items]    
Derivative asset not designated as hedging instrument, Unrealized Appreciation 115,047  
Commodity Contracts [Member] | Receivables On Open Futures Contracts, Unrealized Appreciation On Swap And/ Or Forwards Agreements [Member] | ProShares Ultra DJ-UBS Natural Gas [Member]
    
Derivative Instruments, Gain (Loss) [Line Items]    
Derivative asset not designated as hedging instrument, Unrealized Appreciation 14,044,618 [1]  
Commodity Contracts [Member] | Receivables On Open Futures Contracts, Unrealized Appreciation On Swap And/ Or Forwards Agreements [Member] | ProShares Ultra Gold [Member]
    
Derivative Instruments, Gain (Loss) [Line Items]    
Derivative asset not designated as hedging instrument, Unrealized Appreciation 9,223,820 [1]  
Commodity Contracts [Member] | Receivables On Open Futures Contracts, Unrealized Appreciation On Swap And/ Or Forwards Agreements [Member] | ProShares Ultra DJ-UBS Crude Oil [Member]
    
Derivative Instruments, Gain (Loss) [Line Items]    
Derivative asset not designated as hedging instrument, Unrealized Appreciation 26,556,087 [1] 55,294,030 [1]
Foreign Exchange Contracts [Member] | Unrealized Depreciation On Foreign Currency Forward Contracts And Payable On Open Futures Contracts [Member] | ProShares UltraShort Australian Dollar [Member]
    
Derivative Instruments, Gain (Loss) [Line Items]    
Derivative liability not designated as hedging instrument, Unrealized Depreciation 109,570 [1]  
Foreign Exchange Contracts [Member] | Unrealized Depreciation On Foreign Currency Forward Contracts And Payable On Open Futures Contracts [Member] | ProShares UltraShort Euro [Member]
    
Derivative Instruments, Gain (Loss) [Line Items]    
Derivative liability not designated as hedging instrument, Unrealized Depreciation 1,439,211 13,398,619
Foreign Exchange Contracts [Member] | Unrealized Depreciation On Foreign Currency Forward Contracts And Payable On Open Futures Contracts [Member] | ProShares Ultra Euro [Member]
    
Derivative Instruments, Gain (Loss) [Line Items]    
Derivative liability not designated as hedging instrument, Unrealized Depreciation 137,134 2,314
Foreign Exchange Contracts [Member] | Unrealized Depreciation On Foreign Currency Forward Contracts And Payable On Open Futures Contracts [Member] | ProShares Ultra Yen [Member]
    
Derivative Instruments, Gain (Loss) [Line Items]    
Derivative liability not designated as hedging instrument, Unrealized Depreciation 70,562 507,819
Foreign Exchange Contracts [Member] | Unrealized Depreciation On Foreign Currency Forward Contracts And Payable On Open Futures Contracts [Member] | ProShares Short Euro [Member]
    
Derivative Instruments, Gain (Loss) [Line Items]    
Derivative liability not designated as hedging instrument, Unrealized Depreciation   55,056 [1]
Foreign Exchange Contracts [Member] | Unrealized Depreciation On Foreign Currency Forward Contracts And Payable On Open Futures Contracts [Member] | ProShares UltraShort Yen [Member]
    
Derivative Instruments, Gain (Loss) [Line Items]    
Derivative liability not designated as hedging instrument, Unrealized Depreciation   232,642
Foreign Exchange Contracts [Member] | Unrealized Depreciation On Foreign Currency Forward Contracts And Payable On Open Futures Contracts [Member] | ProShares Ultra Australian Dollar [Member]
    
Derivative Instruments, Gain (Loss) [Line Items]    
Derivative liability not designated as hedging instrument, Unrealized Depreciation   99,030 [1]
Foreign Exchange Contracts [Member] | Unrealized Appreciation On Foreign Currency Forward Contracts And Receivables On Open Futures Contracts [Member] | ProShares UltraShort Australian Dollar [Member]
    
Derivative Instruments, Gain (Loss) [Line Items]    
Derivative asset not designated as hedging instrument, Unrealized Appreciation   85,590 [1]
Foreign Exchange Contracts [Member] | Unrealized Appreciation On Foreign Currency Forward Contracts And Receivables On Open Futures Contracts [Member] | ProShares UltraShort Euro [Member]
    
Derivative Instruments, Gain (Loss) [Line Items]    
Derivative asset not designated as hedging instrument, Unrealized Appreciation 15,104,660 251,047
Foreign Exchange Contracts [Member] | Unrealized Appreciation On Foreign Currency Forward Contracts And Receivables On Open Futures Contracts [Member] | ProShares Ultra Euro [Member]
    
Derivative Instruments, Gain (Loss) [Line Items]    
Derivative asset not designated as hedging instrument, Unrealized Appreciation 3,138 89,473
Foreign Exchange Contracts [Member] | Unrealized Appreciation On Foreign Currency Forward Contracts And Receivables On Open Futures Contracts [Member] | ProShares Ultra Yen [Member]
    
Derivative Instruments, Gain (Loss) [Line Items]    
Derivative asset not designated as hedging instrument, Unrealized Appreciation   13,523
Foreign Exchange Contracts [Member] | Unrealized Appreciation On Foreign Currency Forward Contracts And Receivables On Open Futures Contracts [Member] | ProShares Short Euro [Member]
    
Derivative Instruments, Gain (Loss) [Line Items]    
Derivative asset not designated as hedging instrument, Unrealized Appreciation 61,713 [1]  
Foreign Exchange Contracts [Member] | Unrealized Appreciation On Foreign Currency Forward Contracts And Receivables On Open Futures Contracts [Member] | ProShares UltraShort Yen [Member]
    
Derivative Instruments, Gain (Loss) [Line Items]    
Derivative asset not designated as hedging instrument, Unrealized Appreciation 2,732,626 38,346,817
Foreign Exchange Contracts [Member] | Unrealized Appreciation On Foreign Currency Forward Contracts And Receivables On Open Futures Contracts [Member] | ProShares Ultra Australian Dollar [Member]
    
Derivative Instruments, Gain (Loss) [Line Items]    
Derivative asset not designated as hedging instrument, Unrealized Appreciation 124,930 [1]  
VIX Futures Contracts [Member] | Payable On Open Futures Contracts, Unrealized Depreciation On Swap And/ Or Forwards Agreement [Member] | ProShares VIX Short-Term Futures ETF [Member]
    
Derivative Instruments, Gain (Loss) [Line Items]    
Derivative liability not designated as hedging instrument, Unrealized Depreciation 8,346,060 [1] 2,590,243 [1]
VIX Futures Contracts [Member] | Payable On Open Futures Contracts, Unrealized Depreciation On Swap And/ Or Forwards Agreement [Member] | ProShares VIX Mid-Term Futures ETF [Member]
    
Derivative Instruments, Gain (Loss) [Line Items]    
Derivative liability not designated as hedging instrument, Unrealized Depreciation 1,876,429 [1] 1,703,570 [1]
VIX Futures Contracts [Member] | Payable On Open Futures Contracts, Unrealized Depreciation On Swap And/ Or Forwards Agreement [Member] | ProShares Ultra VIX Short-Term Futures ETF [Member]
    
Derivative Instruments, Gain (Loss) [Line Items]    
Derivative liability not designated as hedging instrument, Unrealized Depreciation 18,737,121 [1] 1,676,460 [1]
VIX Futures Contracts [Member] | Payable On Open Futures Contracts, Unrealized Depreciation On Swap And/ Or Forwards Agreement [Member] | ProShares Short VIX Short-Term Futures ETF [Member]
    
Derivative Instruments, Gain (Loss) [Line Items]    
Derivative liability not designated as hedging instrument, Unrealized Depreciation   2,014,234 [1]
VIX Futures Contracts [Member] | Receivables On Open Futures Contracts, Unrealized Appreciation On Swap And/ Or Forwards Agreements [Member] | ProShares VIX Short-Term Futures ETF [Member]
    
Derivative Instruments, Gain (Loss) [Line Items]    
Derivative asset not designated as hedging instrument, Unrealized Appreciation   2,368,824 [1]
VIX Futures Contracts [Member] | Receivables On Open Futures Contracts, Unrealized Appreciation On Swap And/ Or Forwards Agreements [Member] | ProShares VIX Mid-Term Futures ETF [Member]
    
Derivative Instruments, Gain (Loss) [Line Items]    
Derivative asset not designated as hedging instrument, Unrealized Appreciation   233,160 [1]
VIX Futures Contracts [Member] | Receivables On Open Futures Contracts, Unrealized Appreciation On Swap And/ Or Forwards Agreements [Member] | ProShares Ultra VIX Short-Term Futures ETF [Member]
    
Derivative Instruments, Gain (Loss) [Line Items]    
Derivative asset not designated as hedging instrument, Unrealized Appreciation   4,034,873 [1]
VIX Futures Contracts [Member] | Receivables On Open Futures Contracts, Unrealized Appreciation On Swap And/ Or Forwards Agreements [Member] | ProShares Short VIX Short-Term Futures ETF [Member]
    
Derivative Instruments, Gain (Loss) [Line Items]    
Derivative asset not designated as hedging instrument, Unrealized Appreciation $ 2,388,716 [1] $ 627,059 [1]
[1] Includes cumulative appreciation/depreciation of futures contracts as reported in the Schedules of Investments. Only current day's variation margin is reported within the Statements of Financial Condition in receivable/payable on open futures contracts.