Fair Value Measurements - Summary of Assets and Liabilities Measured at Fair Value (Detail) - USD ($)	Sep. 30, 2018	Dec. 31, 2017
Assets
Total assets	$ 3,590,656	$ 3,653,141
Liabilities
Total liabilities	1,202,086	1,428,659
Futures Contracts [Member]
Assets
Total assets	3,195,935	2,377,628
Liabilities
Total liabilities	663,783	639,577
Forward Contracts [Member]
Assets
Total assets	394,721	1,275,513
Liabilities
Total liabilities	538,303	789,082
Level 1 [Member]
Assets
Total assets	3,195,935	2,377,628
Liabilities
Total liabilities	663,783	639,577
Level 1 [Member] | Futures Contracts [Member]
Assets
Total assets	3,195,935	2,377,628
Liabilities
Total liabilities	663,783	639,577
Level 2 [Member]
Assets
Total assets	394,721	1,275,513
Liabilities
Total liabilities	538,303	789,082
Level 2 [Member] | Forward Contracts [Member]
Assets
Total assets	394,721	1,275,513
Liabilities
Total liabilities	$ 538,303	$ 789,082