7. FINANCIAL DERIVATIVE INSTRUMENTS - Fair value of derivative contracts (Details) - Futures Contracts [Member] - USD ($)		Sep. 30, 2019	Dec. 31, 2018
Asset Derivatives Fair Value, Futures Contracts	[1]	$ 139,720	$ 69,626
Liability Derivatives Fair Value, Futures Contracts	[1]	(55,728)	(167,374)
Net Fair Value, Futures Contracts	[1]	83,992	(97,748)
Currencies [Member]
Asset Derivatives Fair Value, Futures Contracts	[1]	15,650	5,351
Liability Derivatives Fair Value, Futures Contracts	[1]	(1,578)	(6,611)
Net Fair Value, Futures Contracts	[1]	14,072	(1,260)
Energy [Member]
Asset Derivatives Fair Value, Futures Contracts	[1]	20,848	0
Liability Derivatives Fair Value, Futures Contracts	[1]	(1,803)	(60,238)
Net Fair Value, Futures Contracts	[1]	19,045	(60,238)
Interest Rates [Member]
Asset Derivatives Fair Value, Futures Contracts	[1]	8,011	30,959
Liability Derivatives Fair Value, Futures Contracts	[1]	(24,422)	(4,148)
Net Fair Value, Futures Contracts	[1]	(16,411)	26,811
Metals [Member]
Asset Derivatives Fair Value, Futures Contracts	[1]	84,935	15,310
Liability Derivatives Fair Value, Futures Contracts	[1]	0	0
Net Fair Value, Futures Contracts	[1]	84,935	15,310
Stock Indices [Member]
Asset Derivatives Fair Value, Futures Contracts	[1]	5,825	17,604
Liability Derivatives Fair Value, Futures Contracts	[1]	(27,925)	(87,631)
Net Fair Value, Futures Contracts	[1]	(22,100)	(70,027)
Treasury Rates [Member]
Asset Derivatives Fair Value, Futures Contracts	[1]	4,451	402
Liability Derivatives Fair Value, Futures Contracts	[1]	0	(8,746)
Net Fair Value, Futures Contracts	[1]	$ 4,451	$ (8,344)

[1] Futures contracts include settled variation margin.