Cash And Cash Equivalents (Schedule Of Cash And Cash Equivalents, Including Restricted Amounts) (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018	Sep. 30, 2018	Dec. 31, 2017
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	$ 403	$ 153
Restricted cash and cash equivalents	29	21
Other non-current assets	1	1
Cash and cash equivalents, including restricted amounts	433	175	$ 366	$ 204
Consumers Energy Company
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	259	39
Restricted cash and cash equivalents	25	17
Cash and cash equivalents, including restricted amounts	$ 284	$ 56	$ 38	$ 65