Statements of Financial Condition (Parenthetical) - USD ($)	Dec. 31, 2019	Dec. 31, 2018
Investments in Securities, Cost	$ 229,340,530	$ 511,790,491
US Treasury Bill Securities [Member]
Investments in Securities, Cost	123,597,579	409,385,046
Affiliated Investments [Member]
Affiliated Investments, at Cost	$ 105,742,951	$ 102,405,445