Service Providers and Related Party Agreements - Additional Information (Detail) - USD ($)		3 Months Ended	9 Months Ended
	Feb. 26, 2015	Sep. 30, 2016	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015	Dec. 31, 2014
Related Party Transaction [Line Items]
Management fee percentage per annum of daily net asset			0.75%
Managing owner waived fees		$ 8,522	$ 8,522
Compensation for service to advisors			0
United States Treasury Obligations		$ 700,927,362	$ 700,927,362		$ 1,077,913,905	$ 1,006,974,568
Cash held by commodity broker						$ 18,108,522
Cash transfer to Commodity Broker to satisfy variation margin requirements				$ 55,249,567
Bank of New York Mellon [Member]
Related Party Transaction [Line Items]
Cash transferred to custodian	$ 55,000,000
United States Treasury Obligations transferred to custodian	1,074,986,895
Commodity Broker [Member]
Related Party Transaction [Line Items]
Cash transfer to Commodity Broker to satisfy variation margin requirements	55,249,567
United States Treasury Obligations transferred to Commodity Broker	$ 32,000,000
Through June 20, 2017 [Member]
Related Party Transaction [Line Items]
Management fee waive on net advisory fees, percentage			100.00%