Trading Activities - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Average number of futures contracts traded	7,300	8,438
Average number of metals forward contracts traded	826	834
Average notional value of currency forward contracts	$ 415,107,828	$ 531,535,509