v2.4.1.9

Significant Accounting Policies - Additional Information (Detail) (USD $)	3 Months Ended	12 Months Ended	0 Months Ended
	Mar. 31, 2015	Dec. 31, 2014	Jul. 31, 2014
Significant Accounting Policies [Line Items]
Level III portfolio investments	$ 0ck0001415311_LevelThreePortfolioInvestmentsForSignificantUnobservableInputsFairValue	$ 0ck0001415311_LevelThreePortfolioInvestmentsForSignificantUnobservableInputsFairValue
Minimum [Member] | Volatility Index Fund [Member]
Significant Accounting Policies [Line Items]
Percentage of brokerage commissions exceed variable create/redeem fees			0.02%ck0001415311_PercentageOfBrokerageCommissionsExceedVariableCreateOrRedeemFees / us-gaap_CapitalUnitsByClassAxis = ck0001415311_VolatilityIndexFundMember / us-gaap_RangeAxis = us-gaap_MinimumMember

X

- Definition

Level three portfolio investments for significant unobservable inputs fair value.

+ References

No definition available.

+ Details

Name:	ck0001415311_LevelThreePortfolioInvestmentsForSignificantUnobservableInputsFairValue
Namespace Prefix:	ck0001415311_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

X

- Definition

Percentage of brokerage commissions exceed variable create/redeem fees.

+ References

No definition available.

+ Details

Name:	ck0001415311_PercentageOfBrokerageCommissionsExceedVariableCreateOrRedeemFees
Namespace Prefix:	ck0001415311_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

X

- Details

Name:	ck0001415311_SignificantAccountingPoliciesLineItems
Namespace Prefix:	ck0001415311_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- Details

Name:	us-gaap_RangeAxis=us-gaap_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: