Statements of Financial Condition (Unaudited) (Parenthetical) - USD ($)	Sep. 30, 2019	Dec. 31, 2018
Investments in Securities, cost	$ 1,435,894,371	$ 2,009,415,674
US Treasury Bill Securities [Member]
Investments in Securities, cost	1,119,756,590	1,614,486,381
Affiliated Investments [Member]
Affiliated Investments, at Cost	$ 316,137,781	$ 394,929,293