Cash And Cash Equivalents (Schedule Of Cash And Cash Equivalents, Including Restricted Amounts) (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018	Dec. 31, 2017
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	$ 234	$ 153
Other non-current assets	0	1
Cash and cash equivalents, including restricted amounts	267	175	$ 227	$ 204
Consumers Energy Company
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	37	39
Other non-current assets	0	0
Cash and cash equivalents, including restricted amounts	$ 64	$ 56	$ 146	$ 65