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]
Gain (loss) from trading	$ (17,812,588)	$ 10,699,637	$ (19,389,463)
Commodity [Member]
Derivative [Line Items]
Gain (loss) from trading	(4,944,164)	(671,410)	(22,477,498)
Equity [Member]
Derivative [Line Items]
Gain (loss) from trading	(6,517,413)	27,931,380	(3,793,015)
Currencies [Member]
Derivative [Line Items]
Gain (loss) from trading	(4,275,072)	(10,774,286)	(1,241,179)
Interest Rates [Member]
Derivative [Line Items]
Gain (loss) from trading	$ (2,075,939)	$ (5,786,047)	$ 8,122,229