Summary of Significant Accounting Policies - Summary of Gross and Net Amounts of Offsetting Assets (Detail) - Commodity Futures Contract [Member] - USD ($)	Mar. 31, 2017	Dec. 31, 2016
Offsetting Assets And Liabilities [Line Items]
Gross Amounts of Recognized Assets	$ 141,321,121	$ 168,313,826
Gross Amounts Offset Assets in the Statement of Financial Condition	(97,790,071)	(151,257,853)
Net Amounts of Assets Presented in the Statement of Financial Condition	43,531,050	17,055,973
Assets Net Amount	43,531,050	17,055,973
Gross Amounts of Recognized Liabilities	(97,790,071)	(151,257,853)
Gross Amounts Offset Liabilities in the Statement of Financial Condition	$ 97,790,071	$ 151,257,853