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 | 97,036,966 | | $ 97,036,966 |
Purchases of Shares - Shares | | | 2,400,000 |
Redemption of Shares - Value | (22,904,626) | | $ (22,904,626) |
Redemption of Shares - Shares | | | (600,000) |
Net Increase (Decrease) due to Share Transactions, value | 74,132,340 | | $ 74,132,340 |
Net Increase (Decrease) due to Share Transactions, shares | | | 1,800,000 |
Net Income (Loss) | | | |
Net Investment Income (Loss) | (500,188) | $ (5) | $ (500,183) |
Net Realized Gain (Loss) on United States TreasuryObligations and Commodity Futures Contracts | 841,626 | 8 | 841,618 |
Net Change in Unrealized Gain (Loss) on United States Treasury Obligations and Commodity Futures Contracts | 36,265,343 | 330 | 36,265,013 |
Net Income (Loss) | 36,606,781 | 333 | 36,606,448 |
Net Change in Shareholders' Equity, value | 110,739,121 | 333 | $ 110,738,788 |
Net Change in Shareholders' Equity, shares | | | 1,800,000 |
Balance - Value at Jun. 30, 2016 | 249,503,063 | $ 1,721 | $ 249,501,342 |
Balance - Shares at Jun. 30, 2016 | | 40 | 5,800,000 |
Balance - Value at Mar. 31, 2016 | 217,854,587 | $ 1,614 | $ 217,852,973 |
Balance - Shares at Mar. 31, 2016 | | 40 | 5,400,000 |
Purchases of Shares - Value | 24,316,544 | | $ 24,316,544 |
Purchases of Shares - Shares | | | 600,000 |
Redemption of Shares - Value | (8,393,133) | | $ (8,393,133) |
Redemption of Shares - Shares | | | (200,000) |
Net Increase (Decrease) due to Share Transactions, value | 15,923,411 | | $ 15,923,411 |
Net Increase (Decrease) due to Share Transactions, shares | | | 400,000 |
Net Income (Loss) | | | |
Net Investment Income (Loss) | (279,113) | $ (3) | $ (279,110) |
Net Realized Gain (Loss) on United States TreasuryObligations and Commodity Futures Contracts | 1,068,167 | 10 | 1,068,157 |
Net Change in Unrealized Gain (Loss) on United States Treasury Obligations and Commodity Futures Contracts | 14,936,011 | 100 | 14,935,911 |
Net Income (Loss) | 15,725,065 | 107 | 15,724,958 |
Net Change in Shareholders' Equity, value | 31,648,476 | 107 | $ 31,648,369 |
Net Change in Shareholders' Equity, shares | | | 400,000 |
Balance - Value at Jun. 30, 2016 | 249,503,063 | $ 1,721 | $ 249,501,342 |
Balance - Shares at Jun. 30, 2016 | | 40 | 5,800,000 |
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 | 105,529,537 | | $ 105,529,537 |
Purchases of Shares - Shares | | | 2,600,000 |
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 | (50,427,434) | | $ (50,427,434) |
Net Increase (Decrease) due to Share Transactions, shares | | | (1,400,000) |
Net Income (Loss) | | | |
Net Investment Income (Loss) | (81,285) | $ (1) | $ (81,284) |
Net Realized Gain (Loss) on United States TreasuryObligations and Commodity Futures Contracts | (18,318,933) | (224) | (18,318,709) |
Net Change in Unrealized Gain (Loss) on United States Treasury Obligations and Commodity Futures Contracts | 26,895,060 | 329 | 26,894,731 |
Net Income (Loss) | 8,494,842 | 104 | 8,494,738 |
Net Change in Shareholders' Equity, value | (41,932,592) | 104 | $ (41,932,696) |
Net Change in Shareholders' Equity, shares | | | (1,400,000) |
Balance - Value at Jun. 30, 2017 | 150,670,024 | $ 1,586 | $ 150,668,438 |
Balance - Shares at Jun. 30, 2017 | | 40 | 3,800,000 |
Balance - Value at Mar. 31, 2017 | 144,118,784 | $ 1,601 | $ 144,117,183 |
Balance - Shares at Mar. 31, 2017 | | 40 | 3,600,000 |
Purchases of Shares - Value | 105,529,537 | | $ 105,529,537 |
Purchases of Shares - Shares | | | 2,600,000 |
Redemption of Shares - Value | (95,844,560) | | $ (95,844,560) |
Redemption of Shares - Shares | | | (2,400,000) |
Net Increase (Decrease) due to Share Transactions, value | 9,684,977 | | $ 9,684,977 |
Net Increase (Decrease) due to Share Transactions, shares | | | 200,000 |
Net Income (Loss) | | | |
Net Investment Income (Loss) | 3,963 | | $ 3,963 |
Net Realized Gain (Loss) on United States TreasuryObligations and Commodity Futures Contracts | (8,038,869) | $ (119) | (8,038,750) |
Net Change in Unrealized Gain (Loss) on United States Treasury Obligations and Commodity Futures Contracts | 4,901,169 | 104 | 4,901,065 |
Net Income (Loss) | (3,133,737) | (15) | (3,133,722) |
Net Change in Shareholders' Equity, value | 6,551,240 | (15) | $ 6,551,255 |
Net Change in Shareholders' Equity, shares | | | 200,000 |
Balance - Value at Jun. 30, 2017 | $ 150,670,024 | $ 1,586 | $ 150,668,438 |
Balance - Shares at Jun. 30, 2017 | | 40 | 3,800,000 |