Schedules of Investments (Unaudited) - Investments (Details) - USD ($)		Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018
U.S. Treasury bills, fair value		$ 491,322,390	$ 750,519,365
Other Assets, Less Liabilities		10,224,366	24,823,740
Net Assets		501,546,756	775,343,105	$ 1,232,799,956	$ 1,209,866,609
United States Treasury Bills 1.57% Due 04/07/20 [Member]
U.S. Treasury bills, face amount	[1],[2]	3,755,000
U.S. Treasury bills, fair value	[1],[2]	3,754,958
United States Treasury Bills 1.56% Due 01/07/20 [Member]
U.S. Treasury bills, face amount	[1],[2]		50,000,000
U.S. Treasury bills, fair value	[1],[2]		49,990,521
United States Treasury Bills 0.31%-1.55% Due 04/16/20 [Member]
U.S. Treasury bills, face amount	[1],[2]	139,000,000
U.S. Treasury bills, fair value	[1],[2]	138,995,656
United States Treasury Bills 1.54% - 1.87% Due 01/16/20 [Member]
U.S. Treasury bills, face amount	[1],[2]		85,000,000
U.S. Treasury bills, fair value	[1],[2]		84,953,805
United States Treasury Bills 1.55% - 1.61% Due 04/23/20 [Member]
U.S. Treasury bills, face amount	[1],[2]	55,000,000	55,000,000
U.S. Treasury bills, fair value	[1],[2]	54,998,941	54,737,729
United States Treasury Bills 1.62% Due 01/21/20 [Member]
U.S. Treasury bills, face amount	[1],[2]		50,600,000
U.S. Treasury bills, fair value	[1],[2]		50,560,743
United States Treasury Bills 1.87% due 01/23/20 [Member]
U.S. Treasury bills, face amount	[1],[2]		50,000,000
U.S. Treasury bills, fair value	[1],[2]		49,957,125
United States Treasury Bills 1.51% - 1.54% Due 05/07/20 [Member]
U.S. Treasury bills, face amount	[1],[2]	55,000,000
U.S. Treasury bills, fair value	[1],[2]	54,996,494
United States Treasury Bills 1.55% Due 01/30/20 [Member]
U.S. Treasury bills, face amount	[1],[2]		100,000,000
U.S. Treasury bills, fair value	[1],[2]		99,886,820
United States Treasury Bills 1.55% - 1.57% Due 05/14/20 [Member]
U.S. Treasury bills, face amount	[1],[2]	20,465,000
U.S. Treasury bills, fair value	[1],[2]	20,463,106
United States Treasury Bills 1.56% Due 02/04/20 [Member]
U.S. Treasury bills, face amount	[1],[2]		15,000,000
U.S. Treasury bills, fair value	[1],[2]		14,978,480
United States Treasury Bills 0.47% - 1.55% Due 05/21/20 [Member]
U.S. Treasury bills, face amount	[1],[2]	80,000,000
U.S. Treasury bills, fair value	[1],[2]	79,992,778
United States Treasury Bills 1.88% – 1.93% due 02/06/20 [Member]
U.S. Treasury bills, face amount	[1],[2]		70,000,000
U.S. Treasury bills, fair value	[1],[2]		69,898,597
United States Treasury Bills 1.52% Due 06/11/20 [Member]
U.S. Treasury bills, face amount	[1],[2]	23,150,000
U.S. Treasury bills, fair value	[1],[2]	23,145,822
United States Treasury Bills 1.55% Due 02/13/20 [Member]
U.S. Treasury bills, face amount	[1],[2]		65,000,000
U.S. Treasury bills, fair value	[1],[2]		64,887,198
United States Treasury Bills 1.13% Due 06/25/20 [Member]
U.S. Treasury bills, face amount	[1],[2]	50,000,000
U.S. Treasury bills, fair value	[1],[2]	49,992,150
United States Treasury Bills 1.55% Due 02/20/20 [Member]
U.S. Treasury bills, face amount	[1],[2]		30,000,000
U.S. Treasury bills, fair value	[1],[2]		29,938,138
United States Treasury Bills 1.54% Due 07/02/20 [Member]
U.S. Treasury bills, face amount	[1],[2]	45,000,000
U.S. Treasury bills, fair value	[1],[2]	44,988,500
United States Treasury Bills 1.81% Due 02/27/20 [Member]
U.S. Treasury bills, face amount	[1],[2]		15,000,000
U.S. Treasury bills, fair value	[1],[2]		14,964,767
United States Treasury Bills 1.06% Due 08/06/20 [Member]
U.S. Treasury bills, face amount	[1],[2]	20,000,000
U.S. Treasury bills, fair value	[1],[2]	19,993,985
United States Treasury Bills 1.53% - 1.61% Due 03/12/20 [Member]
U.S. Treasury bills, face amount	[1],[2]		75,000,000
U.S. Treasury bills, fair value	[1],[2]		74,780,885
United States Treasury Bills 1.55% Due 03/26/20 [Member]
U.S. Treasury bills, face amount	[1],[2]		25,000,000
U.S. Treasury bills, fair value	[1],[2]		24,912,048
US Treasury Bill Securities [Member]
U.S. Treasury bills, fair value		$ 491,322,390	750,519,365
United States Treasury Bills 1.55% Due 04/16/20 [Member]
U.S. Treasury bills, face amount	[1],[2]		35,000,000
U.S. Treasury bills, fair value	[1],[2]		34,845,071
United States Treasury Bills 1.51% Due 05/07/20 [Member]
U.S. Treasury bills, face amount	[1],[2]		15,000,000
U.S. Treasury bills, fair value	[1],[2]		14,920,003
United States Treasury Bills 1.55% due 05/14/20 [Member]
U.S. Treasury bills, face amount	[1],[2]		16,400,000
U.S. Treasury bills, fair value	[1],[2]		$ 16,307,435

[1] A portion of the above United States Treasury bills are posted as margin for the Trust's Index Futures positions as described in Note 2D.

[2] Rates shown are discount rates paid at the time of purchase.