Trading Activities - Gross Fair Values of Derivative Instruments of Futures and Forward Contracts Traded (Detail) - USD ($)	Dec. 31, 2018	Dec. 31, 2017
Futures Contracts [Member]
Derivative [Line Items]
Total unrealized appreciation on open contracts	$ 2,636,639	$ 1,027,835
Total unrealized depreciation on open contracts	(664,769)	(471,939)
Net unrealized appreciation (depreciation) on open contracts	1,971,870	555,896
Futures Contracts [Member] | Currencies [Member]
Derivative [Line Items]
Total unrealized appreciation on open contracts	41,947	19,411
Total unrealized depreciation on open contracts	(70,231)	(2,001)
Futures Contracts [Member] | Energy [Member]
Derivative [Line Items]
Total unrealized appreciation on open contracts	647,829	435,850
Total unrealized depreciation on open contracts	(189,364)	(58,505)
Futures Contracts [Member] | Grains [Member]
Derivative [Line Items]
Total unrealized appreciation on open contracts	160,024	105,003
Total unrealized depreciation on open contracts	(29,138)	(9,538)
Futures Contracts [Member] | Indices [Member]
Derivative [Line Items]
Total unrealized appreciation on open contracts	196,704	147,860
Total unrealized depreciation on open contracts	(160,316)	(45,990)
Futures Contracts [Member] | Interest Rates U.S. [Member]
Derivative [Line Items]
Total unrealized appreciation on open contracts	202,570	49,180
Total unrealized depreciation on open contracts	(1,281)	(3,938)
Futures Contracts [Member] | Interest Rates Non-U.S. [Member]
Derivative [Line Items]
Total unrealized appreciation on open contracts	949,077	64,681
Total unrealized depreciation on open contracts	(28,242)	(197,490)
Futures Contracts [Member] | Livestock [Member]
Derivative [Line Items]
Total unrealized appreciation on open contracts	26,050
Total unrealized depreciation on open contracts	(1,765)	(7,560)
Futures Contracts [Member] | Metals [Member]
Derivative [Line Items]
Total unrealized appreciation on open contracts	140,316	105,894
Total unrealized depreciation on open contracts	(36,545)	(72,004)
Futures Contracts [Member] | Softs [Member]
Derivative [Line Items]
Total unrealized appreciation on open contracts	272,122	99,956
Total unrealized depreciation on open contracts	(147,887)	(74,913)
Forward Contracts [Member]
Derivative [Line Items]
Total unrealized appreciation on open contracts	835,975	494,616
Total unrealized depreciation on open contracts	(618,836)	(325,150)
Net unrealized appreciation (depreciation) on open contracts	217,139	169,466
Forward Contracts [Member] | Currencies [Member]
Derivative [Line Items]
Total unrealized appreciation on open contracts	443,534	283,891
Total unrealized depreciation on open contracts	(549,780)	(167,812)
Forward Contracts [Member] | Metals [Member]
Derivative [Line Items]
Total unrealized appreciation on open contracts	392,441	210,725
Total unrealized depreciation on open contracts	$ (69,056)	$ (157,338)