Trading Activities - Offsetting of Derivative Assets and Liabilities (Detail) - USD ($)	Sep. 30, 2019	Dec. 31, 2018
Derivative [Line Items]
Gross Amounts Recognized, Assets	$ 1,472,325	$ 2,079,754
Gross Amounts Offset in the Statements of Financial Condition, Assets	(1,283,138)	(1,745,551)
Amounts Presented in the Statements of Financial Condition, Assets	189,187	334,203
Net Amount, Assets	189,187	334,203
Gross Amounts Recognized, Liabilities	(1,438,006)	(1,754,621)
Gross Amounts Offset in the Statements of Financial Condition, Liabilities	1,283,138	1,745,551
Amounts Presented in the Statements of Financial Condition, Liabilities	(154,868)	(9,070)
Gross Amounts Not Offset in the Statements of Financial Condition, Cash Collateral Received/ Pledged, Liabilities	154,868	9,070
Net fair value	189,187	334,203
Futures Contracts [Member]
Derivative [Line Items]
Gross Amounts Recognized, Assets	906,418	1,456,716
Gross Amounts Offset in the Statements of Financial Condition, Assets	(906,418)	(1,122,513)
Amounts Presented in the Statements of Financial Condition, Assets		334,203
Net Amount, Assets		334,203
Gross Amounts Recognized, Liabilities	(1,061,286)	(1,122,513)
Gross Amounts Offset in the Statements of Financial Condition, Liabilities	906,418	1,122,513
Amounts Presented in the Statements of Financial Condition, Liabilities	(154,868)
Gross Amounts Not Offset in the Statements of Financial Condition, Cash Collateral Received/ Pledged, Liabilities	154,868
Forward Contracts [Member]
Derivative [Line Items]
Gross Amounts Recognized, Assets	565,907	623,038
Gross Amounts Offset in the Statements of Financial Condition, Assets	(376,720)	(623,038)
Amounts Presented in the Statements of Financial Condition, Assets	189,187
Net Amount, Assets	189,187
Gross Amounts Recognized, Liabilities	(376,720)	(632,108)
Gross Amounts Offset in the Statements of Financial Condition, Liabilities	$ 376,720	623,038
Amounts Presented in the Statements of Financial Condition, Liabilities		(9,070)
Gross Amounts Not Offset in the Statements of Financial Condition, Cash Collateral Received/ Pledged, Liabilities		$ 9,070