Consolidated Statements Of Comprehensive Income (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Net Income	$ 81	$ 101	$ 225	$ 168
Retirement benefits liability adjustments, net of tax	1	1	2	2
Unrealized gain (loss) on investments, net of tax	(3)	1	(3)	2
Other Comprehensive Income (Loss)	(2)	2	(1)	4
Comprehensive Income	79	103	224	172
Comprehensive Income Attributable to Noncontrolling Interest	1	1	1	1
Comprehensive Income Attributable to CMS Energy	78	102	223	171
Consumers Energy Company [Member]
Net Income	100	122	262	198
Retirement benefits liability adjustments, net of tax	1		2	1
Unrealized gain (loss) on investments, net of tax	(4)	3
Reclassification adjustments included in net income, net of tax			(3)
Other Comprehensive Income (Loss)	(3)	3	(1)	1
Comprehensive Income	$ 97	$ 125	$ 261	$ 199