Fund Investment Overview - Additional Information (Detail) - USD ($)	6 Months Ended	12 Months Ended
	Jun. 30, 2015	Dec. 31, 2014
Schedule of Investments [Abstract]
Deposits with broker	$ 43,823,219	$ 250,885,301
Percentage of assets held by broker	21.51%	100.00%
Restricted investments	$ 43,823,219	$ 18,366,219
Percentage of holdings considered restricted	21.51%	7.32%