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	$ 851,529	$ 710,148
Total unrealized depreciation on open contracts	(757,896)	(522,665)
Net unrealized appreciation (depreciation) on open contracts	93,633	187,483
Futures Contracts [Member] | Long [Member]
Derivative [Line Items]
Net unrealized appreciation (depreciation) on open contracts	201,796	140,143
Futures Contracts [Member] | Short [Member]
Derivative [Line Items]
Net unrealized appreciation (depreciation) on open contracts	(108,163)	47,340
Options Contracts [Member] | Long [Member]
Derivative [Line Items]
Total unrealized appreciation on open contracts		51,625
Options Contracts [Member] | Short [Member]
Derivative [Line Items]
Total unrealized depreciation on open contracts		(23,000)
Currencies [Member] | Futures Contracts [Member]
Derivative [Line Items]
Total unrealized appreciation on open contracts	117,929	94,211
Total unrealized depreciation on open contracts	(148,721)	(60,036)
Currencies [Member] | Futures Contracts [Member] | Long [Member]
Derivative [Line Items]
Net unrealized appreciation (depreciation) on open contracts	(26,777)	70,786
Currencies [Member] | Futures Contracts [Member] | Short [Member]
Derivative [Line Items]
Net unrealized appreciation (depreciation) on open contracts	(4,015)	(36,611)
Energy [Member] | Futures Contracts [Member]
Derivative [Line Items]
Total unrealized appreciation on open contracts	84,783	214,439
Total unrealized depreciation on open contracts	(103,128)	(39,440)
Energy [Member] | Futures Contracts [Member] | Long [Member]
Derivative [Line Items]
Net unrealized appreciation (depreciation) on open contracts	(96,130)	213,269
Energy [Member] | Futures Contracts [Member] | Short [Member]
Derivative [Line Items]
Net unrealized appreciation (depreciation) on open contracts	77,785	(38,270)
Energy [Member] | Options Contracts [Member] | Long [Member]
Derivative [Line Items]
Total unrealized appreciation on open contracts		43,000
Energy [Member] | Options Contracts [Member] | Short [Member]
Derivative [Line Items]
Total unrealized depreciation on open contracts		(23,000)
Grains [Member] | Futures Contracts [Member]
Derivative [Line Items]
Total unrealized appreciation on open contracts	59,786	69,673
Total unrealized depreciation on open contracts	(116,823)	(17,591)
Grains [Member] | Futures Contracts [Member] | Long [Member]
Derivative [Line Items]
Net unrealized appreciation (depreciation) on open contracts	(84,112)	(14,200)
Grains [Member] | Futures Contracts [Member] | Short [Member]
Derivative [Line Items]
Net unrealized appreciation (depreciation) on open contracts	27,075	66,282
Indices [Member] | Futures Contracts [Member]
Derivative [Line Items]
Total unrealized appreciation on open contracts	188,979	62,560
Total unrealized depreciation on open contracts	(101,999)	(147,661)
Indices [Member] | Futures Contracts [Member] | Long [Member]
Derivative [Line Items]
Net unrealized appreciation (depreciation) on open contracts	78,137	(22,330)
Indices [Member] | Futures Contracts [Member] | Short [Member]
Derivative [Line Items]
Net unrealized appreciation (depreciation) on open contracts	8,843	(62,771)
Interest Rates U.S. [Member] | Futures Contracts [Member]
Derivative [Line Items]
Total unrealized appreciation on open contracts	110,603	14,844
Total unrealized depreciation on open contracts	(100,422)	(5,813)
Interest Rates U.S. [Member] | Futures Contracts [Member] | Long [Member]
Derivative [Line Items]
Net unrealized appreciation (depreciation) on open contracts	106,822
Interest Rates U.S. [Member] | Futures Contracts [Member] | Short [Member]
Derivative [Line Items]
Net unrealized appreciation (depreciation) on open contracts	(96,641)	9,031
Interest Rates Non-U.S. [Member] | Futures Contracts [Member]
Derivative [Line Items]
Total unrealized appreciation on open contracts	239,824	16,572
Total unrealized depreciation on open contracts	(127,847)	(22,410)
Interest Rates Non-U.S. [Member] | Futures Contracts [Member] | Long [Member]
Derivative [Line Items]
Net unrealized appreciation (depreciation) on open contracts	224,279	(19,505)
Interest Rates Non-U.S. [Member] | Futures Contracts [Member] | Short [Member]
Derivative [Line Items]
Net unrealized appreciation (depreciation) on open contracts	(112,302)	13,667
Livestock [Member] | Futures Contracts [Member]
Derivative [Line Items]
Total unrealized appreciation on open contracts	6,430	144,163
Total unrealized depreciation on open contracts	(2,880)	(138,305)
Livestock [Member] | Futures Contracts [Member] | Long [Member]
Derivative [Line Items]
Net unrealized appreciation (depreciation) on open contracts	5,100	(133,257)
Livestock [Member] | Futures Contracts [Member] | Short [Member]
Derivative [Line Items]
Net unrealized appreciation (depreciation) on open contracts	(1,550)	139,115
Metals [Member] | Futures Contracts [Member]
Derivative [Line Items]
Total unrealized appreciation on open contracts	23,688	50,653
Total unrealized depreciation on open contracts	(5,835)	(40,050)
Metals [Member] | Futures Contracts [Member] | Long [Member]
Derivative [Line Items]
Net unrealized appreciation (depreciation) on open contracts	18,336	50,653
Metals [Member] | Futures Contracts [Member] | Short [Member]
Derivative [Line Items]
Net unrealized appreciation (depreciation) on open contracts	(483)	(40,050)
Softs [Member] | Futures Contracts [Member]
Derivative [Line Items]
Total unrealized appreciation on open contracts	19,507	43,033
Total unrealized depreciation on open contracts	(50,241)	(51,359)
Softs [Member] | Futures Contracts [Member] | Long [Member]
Derivative [Line Items]
Net unrealized appreciation (depreciation) on open contracts	(23,859)	(5,273)
Softs [Member] | Futures Contracts [Member] | Short [Member]
Derivative [Line Items]
Net unrealized appreciation (depreciation) on open contracts	$ (6,875)	(3,053)
Softs [Member] | Options Contracts [Member] | Long [Member]
Derivative [Line Items]
Total unrealized appreciation on open contracts		$ 8,625