Cash And Cash Equivalents (Schedule Of Cash And Cash Equivalents, Including Restricted Amounts) (Details) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016	Mar. 31, 2016	Dec. 31, 2015
Cash and cash equivalents	$ 433	$ 235
Restricted cash and cash equivalents	30	19
Other non-current assets		3
Cash and cash equivalents, including restricted amounts	463	257	$ 206	$ 288
Consumers Energy Company [Member]
Cash and cash equivalents	182	131
Restricted cash and cash equivalents	30	19
Other non-current assets		2
Cash and cash equivalents, including restricted amounts	$ 212	$ 152	$ 56	$ 71