Consolidated Statements Of Comprehensive Income (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Net income	$ 149	$ 140	$ 317	$ 376
Income attributable to noncontrolling interests	1	1	2	2
Net income attributable to CMS Energy	148	139	315	374
Retirement benefits liability adjustments, net of tax	1		3	1
Unrealized gain (loss) on investments, net of tax	1	(2)	3	(1)
Other Comprehensive Income	2	(2)	6
Total Comprehensive Income	150	137	321	374
Consumers Energy Company [Member]
Net income	163	155	361	400
Retirement benefits liability adjustments, net of tax	1		2	1
Unrealized gain (loss) on investments, net of tax				(1)
Other Comprehensive Income	1		2
Total Comprehensive Income	$ 164	$ 155	$ 363	$ 400