Cash And Cash Equivalents (Schedule Of Cash And Cash Equivalents, Including Restricted Amounts) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	$ 168	$ 140
Restricted cash and cash equivalents	17	17
Cash and cash equivalents, including restricted amounts	185	157	$ 175	$ 204
Consumers Energy Company
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	20	11
Restricted cash and cash equivalents	15	17
Cash and cash equivalents, including restricted amounts	$ 35	$ 28	$ 56	$ 65