Cash And Cash Equivalents (Schedule Of Cash And Cash Equivalents, Including Restricted Amounts) (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2016
Cash and cash equivalents	$ 195	$ 182
Restricted cash and cash equivalents	26	17
Other non-current assets	6	5
Cash and cash equivalents, including restricted amounts	227	204	$ 463	$ 257
Consumers Energy Company [Member]
Cash and cash equivalents	115	44
Restricted cash and cash equivalents	26	17
Other non-current assets	5	4
Cash and cash equivalents, including restricted amounts	$ 146	$ 65	$ 212	$ 152