Cash And Cash Equivalents (Schedule Of Cash And Cash Equivalents, Including Restricted Amounts) (Details) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020	Mar. 31, 2020	Dec. 31, 2019
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	$ 496	$ 168
Restricted cash and cash equivalents	28	17
Cash and cash equivalents, including restricted amounts	524	185	$ 861	$ 157
Consumers Energy Company
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	9	20
Restricted cash and cash equivalents	25	15
Cash and cash equivalents, including restricted amounts	$ 34	$ 35	$ 628	$ 28