Service Providers and Related Party Agreements - Additional Information (Detail) - USD ($)		3 Months Ended
	Feb. 26, 2015	Mar. 31, 2016		Mar. 31, 2015	Dec. 31, 2015	[1]	Dec. 31, 2014
Related Party Transaction [Line Items]
Management fee percentage per annum of daily net asset		0.75%
United States Treasury Obligations, at fair value (cost $200,922,264 and $133,486,931, respectively)		$ 200,955,950	[1]		$ 133,489,271		$ 149,996,759
Cash held by commodity broker							$ 10,651,900
Cash transfer to Commodity Broker to satisfy variation margin requirements				$ (9,971,010)
Bank of New York Mellon [Member]
Related Party Transaction [Line Items]
Cash transferred to custodian	$ 10,488,749
United States Treasury Obligations transferred to custodian	207,995,237
Commodity Broker [Member]
Related Party Transaction [Line Items]
United States Treasury Obligations transferred to Commodity Broker	40,995,900
Cash transfer to Commodity Broker to satisfy variation margin requirements	$ 9,971,010

[1] $34,994,000 and $24,997,500, respectively is restricted for maintenance margin purposes.