Investments in Affiliates -Summary of Transactions in, and Earnings from, Investments in Affiliates (Detail) - USD ($)	3 Months Ended			12 Months Ended
	Mar. 31, 2021		Mar. 31, 2020	Dec. 31, 2020		Dec. 31, 2019
Investments In And Advances To Affiliates [Line Items]
Beginning Value	$ 245,409,996
United States Treasury Obligations	14,676		$ 89,994
Ending Value	232,267,665			$ 245,409,996
Affiliated Investments [Member]
Investments In And Advances To Affiliates [Line Items]
Beginning Value	245,409,996		105,630,007	105,630,007
Purchases at Cost				313,642,227		$ 878,991,288
Proceeds from Sales				(326,791,638)		(139,932,933)
United States Treasury Obligations				7,080		492,050
Ending Value	232,267,665		845,180,412	245,409,996		105,630,007
Dividend Income	21,552		712,232
Affiliated Investments [Member] | Exchange-Traded Fund [Member]
Investments In And Advances To Affiliates [Line Items]
Beginning Value	49,876,240	[1]	79,893,780	79,893,780
United States Treasury Obligations				7,080		492,050
Ending Value	49,883,320	[1]	80,385,830	49,876,240	[1]	79,893,780
Dividend Income	7,420		332,997
Affiliated Investments [Member] | Money Market Mutual Fund - Invesco Government & Agency Portfolio, Institutional Class [Member]
Investments In And Advances To Affiliates [Line Items]
Beginning Value			25,736,227	25,736,227
Purchases at Cost						878,991,288
Proceeds from Sales						(139,932,933)
Ending Value	182,384,345	[1],[2]	764,794,582			$ 25,736,227
Dividend Income			$ 379,235
Affiliated Investments [Member] | Money Market Mutual Fund - Invesco Government & Agency Portfolio, Institutional Class [Member] | Money Market Mutual Fund - Invesco Premier U.S. Government Money ETF - Institutional Class [Member]
Investments In And Advances To Affiliates [Line Items]
Beginning Value	195,533,756
Purchases at Cost				313,642,227
Proceeds from Sales				(326,791,638)
Ending Value	182,384,345			$ 195,533,756
Dividend Income	$ 14,132

[1] Affiliated issuer. The issuer and/or the Fund is a wholly-owned subsidiary of Invesco Ltd., or is affiliated by having an investment adviser that is under common control of Invesco Ltd. See Note 8.

[2] The rate shown is the 7-day SEC standardized yield as of March 31, 2021.