Cash And Cash Equivalents (Schedule Of Cash And Cash Equivalents, Including Restricted Amounts) (Details) - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018	Jun. 30, 2018	Dec. 31, 2017
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	$ 312	$ 153
Restricted cash and cash equivalents	22	21
Other non-current assets	0	1
Cash and cash equivalents, including restricted amounts	334	175	$ 501	$ 204
Consumers Energy Company
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	196	39
Restricted cash and cash equivalents	16	17
Cash and cash equivalents, including restricted amounts	$ 212	$ 56	$ 276	$ 65