Cash And Cash Equivalents (Schedule Of Restricted Cash Balances) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016	Dec. 31, 2015
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net cash used in investing activities	$ 346	$ 444
Cash and Cash Equivalents, Including Restricted Amounts, End of Period	463	206	$ 257	$ 288
Consumers Energy Company [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net cash used in investing activities	382	425
Cash and Cash Equivalents, Including Restricted Amounts, End of Period	$ 212	56	$ 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		(7)
Cash and Cash Equivalents, Including Restricted Amounts, End of Period		29
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		(8)
Cash and Cash Equivalents, Including Restricted Amounts, End of Period		$ 29