Fair Value Measurements - Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - Fair Value Measured on a Recurring Basis [Member] - USD ($)	Dec. 31, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	$ 5,250,485	$ 9,747,286
Liabilities	6,587,258	3,930,608
Forward Contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	1,880,468	3,276,785
Liabilities	2,164,284	1,985,045
Futures Contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	3,370,017	6,470,501
Liabilities	4,422,974	1,945,563
Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	3,370,017	6,470,501
Liabilities	4,422,974	1,945,563
Level 1 [Member] | Futures Contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	3,370,017	6,470,501
Liabilities	4,422,974	1,945,563
Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	1,880,468	3,276,785
Liabilities	2,164,284	1,985,045
Level 2 [Member] | Forward Contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	1,880,468	3,276,785
Liabilities	$ 2,164,284	$ 1,985,045