Cash And Cash Equivalents (Schedule Of Cash And Cash Equivalents, Including Restricted Amounts) (Details) - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016	Jun. 30, 2016	Dec. 31, 2015
Cash and cash equivalents	$ 418	$ 235
Restricted cash and cash equivalents	17	19
Other non-current assets	6	3
Cash and cash equivalents, including restricted amounts	441	257	$ 406	$ 288
Consumers Energy Company [Member]
Cash and cash equivalents	343	131
Restricted cash and cash equivalents	17	19
Other non-current assets	4	2
Cash and cash equivalents, including restricted amounts	$ 364	$ 152	$ 137	$ 71