Trading Activities - Trading Gains and Losses, by Market Sector, on Derivative Instruments (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Derivative [Line Items]
Total trading results	$ (4,020,509)	$ 2,788,956	$ (8,663,403)
Commodity [Member]
Derivative [Line Items]
Total trading results	(1,138,112)	(1,213,211)	(6,068,586)
Equity [Member]
Derivative [Line Items]
Total trading results	(720,406)	11,348,033	(2,859,526)
Currencies [Member]
Derivative [Line Items]
Total trading results	(482,851)	(4,000,339)	(701,495)
Interest Rates [Member]
Derivative [Line Items]
Total trading results	$ (1,679,140)	$ (3,345,527)	$ 966,204