Consolidated Statements of Comprehensive Income (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Net income	$ 67	$ 135
Retirement benefits liability adjustments	1	0
Unrealized gain (loss) on investments, net of tax	1	0
Other Comprehensive Income	2	0
Total Comprehensive Income	69	135
Consumers Energy Company [Member]
Net income	76	153
Retirement benefits liability adjustments	1	1
Unrealized gain (loss) on investments, net of tax	(3)	(1)
Other Comprehensive Income	(2)	0
Total Comprehensive Income	$ 74	$ 153