Schedule of Investments (Unaudited) - Treasury Bills and Affiliated Investments - USD ($)		3 Months Ended		12 Months Ended
		Mar. 31, 2019		Dec. 31, 2018
Schedule of Investments [Line Items]
Percentage of Shareholders' Equity		101.03%		101.05%
United States Treasury Obligations, Value		$ 361,816,083		$ 405,215,093
Affiliated Investments, Value		97,874,197		94,741,922
Investments in Securities, Value		459,690,280		499,957,015
Investments in Securities, cost		$ 459,583,199		$ 499,901,020
Affiliated Investments [Member]
Schedule of Investments [Line Items]
Percentage of Shareholders' Equity		21.51%		19.15%
Affiliated Investments, Value		$ 97,874,197		$ 94,741,922
Affiliated Investments, at Cost		$ 97,787,532		$ 94,692,742
U.S. Treasury Bills, 2.465% due April 4, 2019 [Member]
Schedule of Investments [Line Items]
Percentage of Shareholders' Equity	[1]	2.20%
United States Treasury Obligations, Value	[1]	$ 9,998,037
United States Treasury Obligations, Principal Value	[1]	$ 10,000,000
Investment Interest Rate	[1]	2.465%
Investment Maturity Date	[1]	Apr. 04, 2019
U.S. Treasury Bills, 2.470% due April 23, 2019 [Member]
Schedule of Investments [Line Items]
Percentage of Shareholders' Equity	[1]	16.68%
United States Treasury Obligations, Value	[1]	$ 75,889,261
United States Treasury Obligations, Principal Value	[1]	$ 76,000,000
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]	36.41%
United States Treasury Obligations, Value	[1],[2]	$ 165,664,974
United States Treasury Obligations, Principal Value	[1],[2]	$ 166,000,000
Investment Interest Rate	[1],[2]	2.375%
Investment Maturity Date	[1],[2]	May 02, 2019
Restricted for maintenance margin		$ 66,559,930
U.S. Treasury Bills, 2.470% due July 11, 2019 [Member]
Schedule of Investments [Line Items]
Percentage of Shareholders' Equity	[1]	24.23%
United States Treasury Obligations, Value	[1]	$ 110,263,811
United States Treasury Obligations, Principal Value	[1]	$ 111,000,000
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	[1]	79.52%		81.90%
United States Treasury Obligations, Value	[1]	$ 361,816,083		$ 405,215,093
Investments in Securities, cost		$ 361,795,667		$ 405,208,278
Exchange-Traded Fund [Member] | Affiliated Investments [Member]
Schedule of Investments [Line Items]
Percentage of Shareholders' Equity	[3]	17.38%		15.98%
Affiliated Investments, Value	[3]	$ 79,085,853		$ 79,048,368
Affiliated Investments, Shares	[3]	749,700		749,700
Affiliated Investments, at Cost	[3]	$ 78,999,188		$ 78,999,188
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		4.13%	[4]	3.17%	[5]
Affiliated Investments, Value		$ 18,788,344	[4]	$ 15,693,554	[5]
Affiliated Investments, Shares		18,788,344	[4]	15,693,554	[5]
Investment Interest Rate		2.33%	[4]	2.30%	[5]
Affiliated Investments, at Cost		$ 18,788,344	[4]	$ 15,693,554	[5]
U.S. Treasury Bills, 2.175% due January 3, 2019 [Member]
Schedule of Investments [Line Items]
Percentage of Shareholders' Equity	[1]			22.43%
United States Treasury Obligations, Value	[1]			$ 110,993,078
United States Treasury Obligations, Principal Value	[1]			$ 111,000,000
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]			28.19%
United States Treasury Obligations, Value	[1]			$ 139,473,264
United States Treasury Obligations, Principal Value	[1]			$ 140,000,000
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]			31.28%
United States Treasury Obligations, Value	[1],[6]			$ 154,748,751
United States Treasury Obligations, Principal Value	[1],[6]			$ 156,000,000
Investment Interest Rate	[1],[6]			2.43%
Investment Maturity Date	[1],[6]			May 02, 2019
Restricted for maintenance margin				$ 66,166,400

[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 $66,559,930 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 $66,166,400 are on deposit with the Commodity Broker and held as maintenance margin for open futures contracts.