Summary of Significant Accounting Policies - Summary of Average Monthly Notional Value of Future Contracts Outstanding (Detail) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Notional Disclosures [Abstract]
Average Notional Value	$ 215,120,550	$ 314,569,045	$ 206,643,140	$ 297,296,490