Trading Activities - Trading Gains and Losses, by Market Sector, on Derivative Instruments (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Derivative [Line Items]
Total trading results	$ 1,606,415	$ (404,021)	$ (221,011)	$ (2,596,643)
Commodity [Member]
Derivative [Line Items]
Total trading results	971,122	(895,166)	132,767	(3,761,340)
Equity [Member]
Derivative [Line Items]
Total trading results	1,236,875	1,728,930	1,118,265	7,564,217
Currencies [Member]
Derivative [Line Items]
Total trading results	(79,098)	179,521	(760,753)	(2,949,031)
Interest Rates [Member]
Derivative [Line Items]
Total trading results	$ (522,484)	$ (1,417,306)	$ (711,290)	$ (3,450,489)