Statement of Changes in Shareholders' Equity - USD ($)	Total	General Shares [Member]	Shares [Member]
Balance - Value at Dec. 31, 2014	$ 133,192,855	$ 1,567	$ 133,191,288
Balance - Shares at Dec. 31, 2014		40	3,400,000
Sale of Shares - Value	74,847,261		$ 74,847,261
Sale of Shares - Shares			1,800,000
Redemption of Shares - Value	(55,704,624)		$ (55,704,624)
Redemption of Shares - Shares			(1,400,000)
Net Increase (Decrease) due to Share Transactions, value	19,142,637		$ 19,142,637
Net Increase (Decrease) due to Share Transactions, shares			400,000
Net Income (Loss)
Net Investment Income (Loss)	(296,123)	$ (1)	$ (296,122)
Net Realized Gain (Loss) on United States Treasury Obligations and Commodity Futures Contracts	(11,689,535)	(17)	(11,689,518)
Net Change in Unrealized Gain (Loss) on United States Treasury Obligations and Commodity Futures Contracts	7,980,343	12	7,980,331
Net Income (Loss)	(4,005,315)	(6)	(4,005,309)
Net Change in Shareholders' Equity, value	15,137,322	(6)	$ 15,137,328
Net Change in Shareholders' Equity, shares			400,000
Balance - Value at Mar. 31, 2015	148,330,177	$ 1,561	$ 148,328,616
Balance - Shares at Mar. 31, 2015		40	3,800,000
Balance - Value at Dec. 31, 2015	138,763,942	$ 1,388	$ 138,762,554
Balance - Shares at Dec. 31, 2015		40	4,000,000
Sale of Shares - Value	72,720,422		$ 72,720,422
Sale of Shares - Shares			1,800,000
Redemption of Shares - Value	(14,511,493)		$ (14,511,493)
Redemption of Shares - Shares			(400,000)
Net Increase (Decrease) due to Share Transactions, value	58,208,929		$ 58,208,929
Net Increase (Decrease) due to Share Transactions, shares			1,400,000
Net Income (Loss)
Net Investment Income (Loss)	(221,075)	$ (2)	$ (221,073)
Net Realized Gain (Loss) on United States Treasury Obligations and Commodity Futures Contracts	(226,541)	(2)	(226,539)
Net Change in Unrealized Gain (Loss) on United States Treasury Obligations and Commodity Futures Contracts	21,329,332	230	21,329,102
Net Income (Loss)	20,881,716	226	20,881,490
Net Change in Shareholders' Equity, value	79,090,645	226	$ 79,090,419
Net Change in Shareholders' Equity, shares			1,400,000
Balance - Value at Mar. 31, 2016	$ 217,854,587	$ 1,614	$ 217,852,973
Balance - Shares at Mar. 31, 2016		40	5,400,000