Schedule of Investments (Unaudited) - Treasury Bills and Money Market Fund - USD ($)		3 Months Ended		12 Months Ended
		Mar. 31, 2019		Dec. 31, 2018
Schedule of Investments [Line Items]
Percentage of Shareholders' Equity		99.47%		103.49%
United States Treasury Obligations, Value		$ 273,523,483		$ 409,384,745
Affiliated Investments, value		99,259,143		102,216,801
Investments in Securities, Value		372,782,626		511,601,546
Investments in Securities, Cost		$ 372,926,198		$ 511,790,491
Affiliated Investments [Member]
Schedule of Investments [Line Items]
Percentage of Shareholders' Equity		26.49%		20.68%
Affiliated Investments, value		$ 99,259,143		$ 102,216,801
Affiliated Investments, at Cost		$ 99,409,937		$ 102,405,445
U.S. Treasury Bills, 2.465% due April 4, 2019 [Member]
Schedule of Investments [Line Items]
Percentage of Shareholders' Equity	[1]	14.14%		10.65%
United States Treasury Obligations, Value	[1]	$ 52,989,593		$ 52,672,055
United States Treasury Obligations, Principal Value	[1]	$ 53,000,000		$ 53,000,000
Investment Interest Rate	[1]	2.465%		2.465%
Investment Maturity Date	[1]	Apr. 04, 2019		Apr. 04, 2019
U.S. Treasury Bills, 2.470% due April 23, 2019 [Member]
Schedule of Investments [Line Items]
Percentage of Shareholders' Equity	[1]	27.71%
United States Treasury Obligations, Value	[1]	$ 103,848,463
United States Treasury Obligations, Principal Value	[1]	$ 104,000,000
Investment Interest Rate	[1]	2.47%
Investment Maturity Date	[1]	Apr. 23, 2019
U.S. Treasury Bills, 2.375% due May 2, 2019 [Member]
Schedule of Investments [Line Items]
Percentage of Shareholders' Equity	[1],[2]	26.63%
United States Treasury Obligations, Value	[1],[2]	$ 99,798,177
United States Treasury Obligations, Principal Value	[1],[2]	$ 100,000,000
Investment Interest Rate	[1],[2]	2.375%
Investment Maturity Date	[1],[2]	May 02, 2019
Restricted for maintenance margin		$ 10,677,530
U.S. Treasury Bills, 2.470% due July 11, 2019 [Member]
Schedule of Investments [Line Items]
Percentage of Shareholders' Equity	[1]	4.50%
United States Treasury Obligations, Value	[1]	$ 16,887,250
United States Treasury Obligations, Principal Value	[1]	$ 17,000,000
Investment Interest Rate	[1]	2.47%
Investment Maturity Date	[1]	Jul. 11, 2019
United States Treasury Obligations [Member]
Schedule of Investments [Line Items]
Percentage of Shareholders' Equity		72.98%		82.81%
United States Treasury Obligations, Value		$ 273,523,483		$ 409,384,745
Investments in Securities, Cost		$ 273,516,261		$ 409,385,046
Exchange-Traded Fund [Member] | Affiliated Investments [Member]
Schedule of Investments [Line Items]
Percentage of Shareholders' Equity	[3]	21.31%		16.15%
Affiliated Investments, value	[3]	$ 79,855,930		$ 79,818,080
Affiliated Investments, Shares	[3]	757,000		757,000
Affiliated Investments, at Cost	[3]	$ 80,006,724		$ 80,006,724
Money Market Mutual Fund - Invesco Premier U.S. Government Money Portfolio - Institutional Class [Member] | Affiliated Investments [Member]
Schedule of Investments [Line Items]
Percentage of Shareholders' Equity		5.18%	[4]	4.53%	[5]
Affiliated Investments, value		$ 19,403,213	[4]	$ 22,398,721	[5]
Affiliated Investments, Shares		19,403,213	[4]	22,398,721	[5]
Investment Interest Rate		2.33%	[4]	2.30%	[5]
Investments in Securities, Cost		$ 19,403,213	[4]	$ 22,398,721	[5]
U.S. Treasury Bills, 2.175% due January 3, 2019 [Member]
Schedule of Investments [Line Items]
Percentage of Shareholders' Equity	[1]			24.68%
United States Treasury Obligations, Value	[1]			$ 121,992,392
United States Treasury Obligations, Principal Value	[1]			$ 122,000,000
Investment Interest Rate	[1]			2.175%
Investment Maturity Date	[1]			Jan. 03, 2019
U.S. Treasury Bills, 2.370% due February 28, 2019 [Member]
Schedule of Investments [Line Items]
Percentage of Shareholders' Equity	[1]			29.02%
United States Treasury Obligations, Value	[1]			$ 143,458,214
United States Treasury Obligations, Principal Value	[1]			$ 144,000,000
Investment Interest Rate	[1]			2.37%
Investment Maturity Date	[1]			Feb. 28, 2019
U.S. Treasury Bills, 2.430% due May 2, 2019 [Member]
Schedule of Investments [Line Items]
Percentage of Shareholders' Equity	[1],[6]			18.46%
United States Treasury Obligations, Value	[1],[6]			$ 91,262,084
United States Treasury Obligations, Principal Value	[1],[6]			$ 92,000,000
Investment Interest Rate	[1],[6]			2.43%
Investment Maturity Date	[1],[6]			May 02, 2019
Restricted for maintenance margin				$ 10,614,400

[1] Security may be traded on a discount basis. The interest rate shown represents the discount rate at the most recent auction date of the security prior to period end.

[2] United States Treasury Obligations of $10,677,530 are on deposit with the Commodity Broker and held as maintenance margin for open futures contracts.

[3] Affiliated company. The security and the Fund are affiliated by having the same investment adviser. See Note 8.

[4] The security and the Fund are advised by wholly-owned subsidiaries of Invesco Ltd. and are therefore considered to be affiliated. The rate shown is the 7-day SEC standardized yield as of March 31, 2019.

[5] The security and the Fund are advised by wholly-owned subsidiaries of Invesco Ltd. and are therefore considered to be affiliated. The rate shown is the 7-day SEC standardized yield as of December 31, 2018.

[6] United States Treasury Obligations of $10,614,400 are on deposit with the Commodity Broker and held as maintenance margin for open futures contracts.