Fund Investment Overview - Additional Information (Detail) (USD $)	6 Months Ended	12 Months Ended
Jun. 30, 2014	Dec. 31, 2013
Schedule Of Investments [Abstract]
Deposits with broker	$ 399,832,379	$ 299,455,287
Percentage of asset held by broker	100.00%	100.00%
Restricted investments	$ 10,993,620	$ 9,318,925
Percentage of holdings considered restricted	2.80%	3.10%

Amount of right to receive cash and securities on deposit with broker-dealers to demonstrate an intention to complete a purchase (good faith deposit) and collateral deposited by counterparty to cover the credit risk assumed (margin deposit).

No definition available.

Name:	us-gaap_GoodFaithAndMarginDepositsWithBrokerDealers
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant