Note 9 - Redeemable Noncontrolling Interests (Details Textual) - USD ($) $ in Millions				12 Months Ended
	Apr. 14, 2020	Jul. 29, 2019	Jun. 22, 2018	Dec. 31, 2020
Temporary Equity, Increase from Sale of Parent Equity Interest				$ 7
Ashwoods [Member] | Hydro-Québec [Member]
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners	45.00%
Temporary Equity, Increase from Sale of Parent Equity Interest	$ 7
TM4 Inc. [Member]
Temporary Equity, Stock Issued During Period, Value, New Issues			$ 102
TM4 Inc. [Member] | Hydro-Québec [Member]
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners			45.00%
S.M.E. S.p.A. [Member] | Hydro-Québec [Member]
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners		45.00%
Prestolite E-Propulsion Systems (Beijing) Limited [Member] | Hydro-Québec [Member]
Minority Interest, Ownership Percentage by Noncontrolling Owners, Increase		22.50%
SME and PEPS [Member]
Temporary Equity, Increase from Sale of Parent Equity Interest		$ 64