Consolidated Statements Of Comprehensive Income (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Net Income	$ 127	$ 149	$ 352	$ 317
Net gain arising during the period, net of tax	10		10
Prior service credit adjustment, net of tax	5		5
Amortization of net actuarial loss, net of tax	1	1	3	3
Unrealized gain (loss) on investments, net of tax	1	1	(2)	3
Other Comprehensive Income (Loss)	17	2	16	6
Comprehensive Income	144	151	368	323
Comprehensive Income Attributable to Noncontrolling Interest	1	1	2	2
Comprehensive Income Attributable to CMS Energy	143	150	366	321
Consumers Energy Company [Member]
Net Income	153	163	415	361
Amortization of net actuarial loss, net of tax		1	2	2
Reclassification adjustments included in net income, net of tax			(3)
Other Comprehensive Income (Loss)		1	(1)	2
Comprehensive Income	$ 153	$ 164	$ 414	$ 363