Other Income and Other Expense (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Regulatory return on capital expenditures	$ 1		$ 17
Return on stranded and security costs	1	3	4
All other	9	13	11
Total other income	11	16	32
Donations	(11)	(11)	(6)
Civic and political expenditures	(17)	(3)	(3)
All other	(5)	(7)	(7)
Total other expense	(33)	(22)	(24)
Consumers Energy Company [Member]
Regulatory return on capital expenditures	1		17
Return on stranded and security costs	1	3	4
All other	9	12	10
Total other income	16	19	31
Donations	(11)	(11)	(6)
Civic and political expenditures	(17)	(3)	(3)
All other	(5)	(6)	(6)
Total other expense	(33)	(20)	(15)
Investment in CMS Energy common stock [Member] | Consumers Energy Company [Member]
Gain on investment	5	4
Loss on Reaquired and Extinguished Debt [Member]
Gain (Loss) on extinguishment of debt		$ (1)	$ (8)