Trading Activities - Additional Information (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Average number of futures contracts traded	1,730	2,329	1,721	2,260
Average number of metal forward contracts traded	34	34	38	46
Average notional value of currency forward contracts	$ 27,550,044	$ 32,417,598	$ 29,106,570	$ 28,949,146