Investments - Effect of Derivative Instruments on Statements of Operations (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Derivative Instruments, Gain (Loss) [Line Items]
Realized Gain (Loss) on Derivatives Recognized in Income	$ (1,319,878,684)	$ (1,164,748,605)	$ (160,205,460)
Change in Unrealized Appreciation or Depreciation on Derivatives Recognized in Income	157,908,519	(39,455,078)	(46,383,766)
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]
Derivative Instruments, Gain (Loss) [Line Items]
Realized Gain (Loss) on Derivatives Recognized in Income	(195,475,791)	(19,408,543)	(694,347)
Change in Unrealized Appreciation or Depreciation on Derivatives Recognized in Income	609,973	(7,343,245)	22,917,306
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]
Derivative Instruments, Gain (Loss) [Line Items]
Realized Gain (Loss) on Derivatives Recognized in Income	(11,085,506)	(3,335,936)	(14,378,810)
Change in Unrealized Appreciation or Depreciation on Derivatives Recognized in Income	(943,885)	(605,025)	5,157,354
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]
Derivative Instruments, Gain (Loss) [Line Items]
Realized Gain (Loss) on Derivatives Recognized in Income	440,391,389	69,793,028	76,925,998
Change in Unrealized Appreciation or Depreciation on Derivatives Recognized in Income	(21,056,026)	27,098,564	(24,469,104)
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]
Derivative Instruments, Gain (Loss) [Line Items]
Realized Gain (Loss) on Derivatives Recognized in Income	(1,567,340,688)	(392,174,228)	(139,412,525)
Change in Unrealized Appreciation or Depreciation on Derivatives Recognized in Income	(19,866,703)	(27,690,787)	63,595,164
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 Bloomberg Crude Oil [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Realized Gain (Loss) on Derivatives Recognized in Income	(67,752,164)	91,670,324	99,327,097
Change in Unrealized Appreciation or Depreciation on Derivatives Recognized in Income	(22,510,865)	(33,947,511)	46,390,353
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 Bloomberg Natural Gas [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Realized Gain (Loss) on Derivatives Recognized in Income	586,860	15,212,804	8,791,719
Change in Unrealized Appreciation or Depreciation on Derivatives Recognized in Income	1,989,133	(6,412,629)	2,899,165
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]
Derivative Instruments, Gain (Loss) [Line Items]
Realized Gain (Loss) on Derivatives Recognized in Income	(12,240,751)	12,707,635	(5,316,482)
Change in Unrealized Appreciation or Depreciation on Derivatives Recognized in Income	1,238,384	4,101,460	(7,934,871)
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]
Derivative Instruments, Gain (Loss) [Line Items]
Realized Gain (Loss) on Derivatives Recognized in Income	(17,554,714)	10,759,545	15,114,883
Change in Unrealized Appreciation or Depreciation on Derivatives Recognized in Income	(3,372,693)	4,187,736	2,810,170
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 Bloomberg Crude Oil [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Realized Gain (Loss) on Derivatives Recognized in Income	74,061,040	(896,177,096)	(243,325,957)
Change in Unrealized Appreciation or Depreciation on Derivatives Recognized in Income	151,001,639	32,549,981	(125,240,438)
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 Bloomberg Natural Gas [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Realized Gain (Loss) on Derivatives Recognized in Income	17,571,809	(100,776,817)	(6,464,796)
Change in Unrealized Appreciation or Depreciation on Derivatives Recognized in Income	(3,776,159)	41,202,162	(31,232,744)
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]
Derivative Instruments, Gain (Loss) [Line Items]
Realized Gain (Loss) on Derivatives Recognized in Income	5,816,565	(18,605,815)	(9,674,333)
Change in Unrealized Appreciation or Depreciation on Derivatives Recognized in Income	(2,194,272)	(4,311,529)	8,883,268
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]
Derivative Instruments, Gain (Loss) [Line Items]
Realized Gain (Loss) on Derivatives Recognized in Income	62,342,441	(78,309,309)	(155,551,420)
Change in Unrealized Appreciation or Depreciation on Derivatives Recognized in Income	1,566,582	(10,173,451)	(9,889,600)
Foreign Exchange Contracts [Member] | Net realized gain (loss) on futures and/or foreign currency forward contracts/changes in unrealized appreciation/ depreciation on futures and/or foreign currency forward contracts [Member] | ProShares Short Euro [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Realized Gain (Loss) on Derivatives Recognized in Income	663,774	1,559,425	1,593,048
Change in Unrealized Appreciation or Depreciation on Derivatives Recognized in Income	(110,538)	(141,893)	418,562
Foreign Exchange Contracts [Member] | Net realized gain (loss) on futures and/or foreign currency forward contracts/changes in unrealized appreciation/ depreciation on futures and/or foreign currency forward contracts [Member] | ProShares UltraShort Australian Dollar [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Realized Gain (Loss) on Derivatives Recognized in Income	(2,787,204)	4,330,463	2,296,216
Change in Unrealized Appreciation or Depreciation on Derivatives Recognized in Income	1,602,610	(1,163,751)	(174,124)
Foreign Exchange Contracts [Member] | Net realized gain (loss) on futures and/or foreign currency forward contracts/changes in unrealized appreciation/ depreciation on futures and/or foreign currency forward contracts [Member] | ProShares UltraShort Euro [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Realized Gain (Loss) on Derivatives Recognized in Income	(25,711,518)	131,651,572	83,678,955
Change in Unrealized Appreciation or Depreciation on Derivatives Recognized in Income	44,873,267	(45,473,330)	30,511,501
Foreign Exchange Contracts [Member] | Net realized gain (loss) on futures and/or foreign currency forward contracts/changes in unrealized appreciation/ depreciation on futures and/or foreign currency forward contracts [Member] | ProShares UltraShort Yen [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Realized Gain (Loss) on Derivatives Recognized in Income	(22,220,271)	8,809,464	127,846,225
Change in Unrealized Appreciation or Depreciation on Derivatives Recognized in Income	30,640,389	(12,316,677)	(30,965,459)
Foreign Exchange Contracts [Member] | Net realized gain (loss) on futures and/or foreign currency forward contracts/changes in unrealized appreciation/ depreciation on futures and/or foreign currency forward contracts [Member] | ProShares Ultra Euro [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Realized Gain (Loss) on Derivatives Recognized in Income	138,959	(1,982,208)	(420,533)
Change in Unrealized Appreciation or Depreciation on Derivatives Recognized in Income	(1,178,930)	708,291	(204,333)
Foreign Exchange Contracts [Member] | Net realized gain (loss) on futures and/or foreign currency forward contracts/changes in unrealized appreciation/ depreciation on futures and/or foreign currency forward contracts [Member] | ProShares Ultra Yen [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Realized Gain (Loss) on Derivatives Recognized in Income	717,086	(472,913)	(540,398)
Change in Unrealized Appreciation or Depreciation on Derivatives Recognized in Income	$ (603,387)	$ 276,556	$ 144,064