Cash And Cash Equivalents (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Cash and cash equivalents	$ 235	$ 266
Restricted cash and cash equivalents	19	19
Other non-current assets	3	3
Cash and cash equivalents, including restricted amounts	257	288	$ 249	$ 204
Consumers Energy Company [Member]
Cash and cash equivalents	131	50
Restricted cash and cash equivalents	19	19
Other non-current assets	2	2
Cash and cash equivalents, including restricted amounts	$ 152	$ 71	$ 112	$ 49