Cash And Cash Equivalents (Schedule Of Restricted Cash Balances) (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016	Dec. 31, 2015
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net cash used in investing activities	$ (806)	$ (911)
Cash and Cash Equivalents, Including Restricted Amounts, End of Period	441	406	$ 257	$ 288
Consumers Energy Company [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net cash used in investing activities	(802)	(865)
Cash and Cash Equivalents, Including Restricted Amounts, End of Period	$ 364	137	$ 152	$ 71
New Accounting Pronouncement, Early Adoption, Effect [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net cash used in investing activities		(1)
Cash and Cash Equivalents, Including Restricted Amounts, End of Period		21
New Accounting Pronouncement, Early Adoption, Effect [Member] | Consumers Energy Company [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net cash used in investing activities		(1)
Cash and Cash Equivalents, Including Restricted Amounts, End of Period		$ 20