Level three portfolio investments for significant unobservable inputs fair value.

No definition available.

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

Significant Accounting Policies - Additional Information (Detail) - USD ($)		12 Months Ended
	Jul. 31, 2014	Dec. 31, 2016	Dec. 31, 2015
Significant Accounting Policies [Line Items]
Level III portfolio investments		$ 0	$ 0
Minimum [Member] \| Volatility Index Fund [Member]
Significant Accounting Policies [Line Items]
Percentage of brokerage commissions exceed variable create/redeem fees	0.02%