Statement of Changes in Shareholders' Equity - USD ($) | Total | General Shares [Member] | Shares [Member] |
Balance - Value at Dec. 31, 2015 | $ 138,763,942 | $ 1,388 | $ 138,762,554 |
Balance - Shares at Dec. 31, 2015 | | 40 | 4,000,000 |
Purchases of Shares - Value | 123,193,564 | | $ 123,193,564 |
Purchases of Shares - Shares | | | 3,000,000 |
Redemption of Shares - Value | (73,850,136) | | $ (73,850,136) |
Redemption of Shares - Shares | | | (1,800,000) |
Net Increase (Decrease) due to Share Transactions, value | 49,343,428 | | $ 49,343,428 |
Net Increase (Decrease) due to Share Transactions, shares | | | 1,200,000 |
Net Income (Loss) | | | |
Net Investment Income (Loss) | (816,619) | $ (8) | $ (816,611) |
Net Realized Gain (Loss) on United States Treasury Obligations, Affiliated Investments and Commodity Futures Contracts | 34,658,540 | 329 | 34,658,211 |
Net Change in Unrealized Gain (Loss) on United States Treasury Obligations, Affiliated Investments and Commodity Futures Contracts | (815,205) | (8) | (815,197) |
Net Income (Loss) | 33,026,716 | 313 | 33,026,403 |
Net Change in Shareholders' Equity, value | 82,370,144 | 313 | $ 82,369,831 |
Net Change in Shareholders' Equity, shares | | | 1,200,000 |
Balance - Value at Sep. 30, 2016 | 221,134,086 | $ 1,701 | $ 221,132,385 |
Balance - Shares at Sep. 30, 2016 | | 40 | 5,200,000 |
Balance - Value at Jun. 30, 2016 | 249,503,063 | $ 1,721 | $ 249,501,342 |
Balance - Shares at Jun. 30, 2016 | | 40 | 5,800,000 |
Purchases of Shares - Value | 26,156,598 | | $ 26,156,598 |
Purchases of Shares - Shares | | | 600,000 |
Redemption of Shares - Value | (50,945,510) | | $ (50,945,510) |
Redemption of Shares - Shares | | | (1,200,000) |
Net Increase (Decrease) due to Share Transactions, value | (24,788,912) | | $ (24,788,912) |
Net Increase (Decrease) due to Share Transactions, shares | | | (600,000) |
Net Income (Loss) | | | |
Net Investment Income (Loss) | (316,431) | $ (3) | $ (316,428) |
Net Realized Gain (Loss) on United States Treasury Obligations, Affiliated Investments and Commodity Futures Contracts | 33,816,914 | 321 | 33,816,593 |
Net Change in Unrealized Gain (Loss) on United States Treasury Obligations, Affiliated Investments and Commodity Futures Contracts | (37,080,548) | (338) | (37,080,210) |
Net Income (Loss) | (3,580,065) | (20) | (3,580,045) |
Net Change in Shareholders' Equity, value | (28,368,977) | (20) | $ (28,368,957) |
Net Change in Shareholders' Equity, shares | | | (600,000) |
Balance - Value at Sep. 30, 2016 | 221,134,086 | $ 1,701 | $ 221,132,385 |
Balance - Shares at Sep. 30, 2016 | | 40 | 5,200,000 |
Balance - Value at Dec. 31, 2016 | 192,602,616 | $ 1,482 | $ 192,601,134 |
Balance - Shares at Dec. 31, 2016 | | 40 | 5,200,000 |
Purchases of Shares - Value | 147,993,274 | | $ 147,993,274 |
Purchases of Shares - Shares | | | 3,600,000 |
Redemption of Shares - Value | (155,956,971) | | $ (155,956,971) |
Redemption of Shares - Shares | | | (4,000,000) |
Net Increase (Decrease) due to Share Transactions, value | (7,963,697) | | $ (7,963,697) |
Net Increase (Decrease) due to Share Transactions, shares | | | (400,000) |
Net Income (Loss) | | | |
Net Investment Income (Loss) | 25,350 | | $ 25,350 |
Net Realized Gain (Loss) on United States Treasury Obligations, Affiliated Investments and Commodity Futures Contracts | (27,113,650) | $ (361) | (27,113,289) |
Net Change in Unrealized Gain (Loss) on United States Treasury Obligations, Affiliated Investments and Commodity Futures Contracts | 38,357,883 | 511 | 38,357,372 |
Net Income (Loss) | 11,269,583 | 150 | 11,269,433 |
Net Change in Shareholders' Equity, value | 3,305,886 | 150 | $ 3,305,736 |
Net Change in Shareholders' Equity, shares | | | (400,000) |
Balance - Value at Sep. 30, 2017 | 195,908,502 | $ 1,632 | $ 195,906,870 |
Balance - Shares at Sep. 30, 2017 | | 40 | 4,800,000 |
Balance - Value at Jun. 30, 2017 | 150,670,024 | $ 1,586 | $ 150,668,438 |
Balance - Shares at Jun. 30, 2017 | | 40 | 3,800,000 |
Purchases of Shares - Value | 42,463,737 | | $ 42,463,737 |
Purchases of Shares - Shares | | | 1,000,000 |
Net Increase (Decrease) due to Share Transactions, value | 42,463,737 | | $ 42,463,737 |
Net Increase (Decrease) due to Share Transactions, shares | | | 1,000,000 |
Net Income (Loss) | | | |
Net Investment Income (Loss) | 106,635 | $ 1 | $ 106,634 |
Net Realized Gain (Loss) on United States Treasury Obligations, Affiliated Investments and Commodity Futures Contracts | (8,794,717) | (137) | (8,794,580) |
Net Change in Unrealized Gain (Loss) on United States Treasury Obligations, Affiliated Investments and Commodity Futures Contracts | 11,462,823 | 182 | 11,462,641 |
Net Income (Loss) | 2,774,741 | 46 | 2,774,695 |
Net Change in Shareholders' Equity, value | 45,238,478 | 46 | $ 45,238,432 |
Net Change in Shareholders' Equity, shares | | | 1,000,000 |
Balance - Value at Sep. 30, 2017 | $ 195,908,502 | $ 1,632 | $ 195,906,870 |
Balance - Shares at Sep. 30, 2017 | | 40 | 4,800,000 |