Income Taxes (Schedule Of Effective Income Tax Rate Reconciliation) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Taxes [Line Items]
Income from continuing operataions before income taxes	$ 729	$ 756	$ 622
Income from continuing operations before income taxes	727	754	620
Income tax expense at statutory rate	254	264	217
State and local income taxes, net of federal effect	36	37	27
Accelerated flow-through of regulatory tax benefits	(39)
Other, net	(1)	1	1
Income Tax Expense	250	302	245
Effective income tax rate	34.40%	40.10%	39.50%
Consumers Energy Company [Member]
Income Taxes [Line Items]
Income from continuing operataions before income taxes	873	880	736
Income tax expense at statutory rate	306	308	258
State and local income taxes, net of federal effect	42	43	36
Accelerated flow-through of regulatory tax benefits	(39)
Other, net	(3)	(5)	3
Income Tax Expense	$ 306	$ 346	$ 297
Effective income tax rate	35.10%	39.30%	40.40%