v2.4.1.9
Creation and Redemption of Creation Units - Additional Information (Detail)
 3 Months Ended
Mar. 31, 2015
Creation And Redemption Of Creation Units [Line Items]  
Creation Unit, block Shares of a Fund 50,000ck0001415311_CreationUnitBlockSharesOfFund
Fixed transaction fee per Creation Unit 500ck0001415311_FixedTransactionFeePerCreationUnit
Variable transaction fee, percent of the value of the Creation Unit, maximum 0.10%ck0001415311_VariableTransactionFeePercentOfValueOfCreationUnitMaximum
Managed Futures Fund [Member]  
Creation And Redemption Of Creation Units [Line Items]  
Creation Unit, block Shares of a Fund 50,000ck0001415311_CreationUnitBlockSharesOfFund
/ us-gaap_InvestmentTypeAxis
= ck0001415311_ManagedFuturesFundMember
Volatility Index Fund [Member]  
Creation And Redemption Of Creation Units [Line Items]  
Creation Unit, block Shares of a Fund 25,000ck0001415311_CreationUnitBlockSharesOfFund
/ us-gaap_CapitalUnitsByClassAxis
= ck0001415311_VolatilityIndexFundMember
Variable transaction fee, percent of the value of the Creation Unit, maximum 0.05%ck0001415311_VariableTransactionFeePercentOfValueOfCreationUnitMaximum
/ us-gaap_CapitalUnitsByClassAxis
= ck0001415311_VolatilityIndexFundMember