Income Taxes (Schedule Of Effective Income Tax Rate Reconciliation) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Taxes [Line Items]
Income from continuing operataions before income taxes		$ 826	$ 796	$ 729
Income tax expense at statutory rate		289	279	255
State and local income taxes, net of federal effect		37	39	36
Accelerated flow-through of regulatory tax benefits	[1]	(39)	(39)	(39)
Employee share-based awards	[2]	(7)
Other, net		(7)	(8)	(2)
Income Tax Expense		$ 273	$ 271	$ 250
Effective tax rate		33.10%	34.00%	34.30%
Consumers Energy Company [Member]
Income Taxes [Line Items]
Income from continuing operataions before income taxes		$ 936	$ 896	$ 873
Income tax expense at statutory rate		328	314	306
State and local income taxes, net of federal effect		44	42	42
Accelerated flow-through of regulatory tax benefits	[1]	(39)	(39)	(39)
Employee share-based awards	[2]	(6)
Other, net		(7)	(15)	(3)
Income Tax Expense		$ 320	$ 302	$ 306
Effective tax rate		34.20%	33.70%	35.10%

[1] Since 2014, Consumers has followed a regulatory treatment ordered by the MPSC that accelerates the return of certain income tax benefits to customers. This change, which also accelerates Consumers' recognition of the income tax benefits, reduced Consumers' income tax expense by $39 million for each of the years ended December 31, 2016, 2015, and 2014.

[2] CMS Energy and Consumers elected to adopt ASU 2016-09, Improvements to Employee Share-Based Payment Accounting, as of January 1, 2016. For further details on the implementation of this standard, see Note 2, New Accounting Standards.