Statements of Financial Condition (Unaudited) (Parenthetical) - USD ($)	Jun. 30, 2017	Dec. 31, 2016
Investments, cost	$ 1,717,876,964	$ 2,534,934,371
US Treasury Bill Securities [Member]
Investments, cost	1,371,851,699	2,403,904,566
Affiliated Investments [Member]
Affiliated Investments, at Cost	$ 346,025,265	$ 131,029,805