Trading Activities - Additional Information (Detail) - Weighted Average [Member]	3 Months Ended		9 Months Ended
	Sep. 30, 2018 USD ($) Contract	Sep. 30, 2017 USD ($) Contract	Sep. 30, 2018 USD ($) Contract	Sep. 30, 2017 USD ($) Contract
Futures Contracts [Member]
Trading Activity, Gains and Losses, Net [Line Items]
Average number of derivative contracts traded	3,522	3,880	3,313	4,419
Forward Contracts [Member] | Commodity [Member] | Metals [Member]
Trading Activity, Gains and Losses, Net [Line Items]
Average number of derivative contracts traded	294	547	378	553
Forward Contracts [Member] | Currencies [Member]
Trading Activity, Gains and Losses, Net [Line Items]
Average notional value of derivative | $	$ 77,621,980	$ 146,467,394	$ 99,889,209	$ 144,212,140