Cash And Cash Equivalents (Schedule Of Cash And Cash Equivalents, Including Restricted Amounts) (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	$ 153	$ 182
Restricted cash and cash equivalents	21	17
Other non‑current assets	1	5
Cash and cash equivalents, including restricted amounts	175	204	$ 257	$ 288
Consumers Energy Company
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	39	44
Restricted cash and cash equivalents	17	17
Other non‑current assets	0	4
Cash and cash equivalents, including restricted amounts	$ 56	$ 65	$ 152	$ 71