Cash And Cash Equivalents (Schedule Of Cash And Cash Equivalents, Including Restricted Amounts) (Details) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020	Sep. 30, 2020	Dec. 31, 2019
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	$ 102	$ 32
Restricted cash and cash equivalents	30	17
Cash and cash equivalents, including restricted amounts	236	185	$ 558	$ 157
Discontinued Operations, Held-for-sale
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	104	136
Consumers Energy Company
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	29	20
Restricted cash and cash equivalents	26	15
Cash and cash equivalents, including restricted amounts	$ 55	$ 35	$ 223	$ 28