Income Taxes (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012 Consumers Energy Company [Member]	Sep. 30, 2011 Consumers Energy Company [Member]	Sep. 30, 2012 Consumers Energy Company [Member]	Sep. 30, 2011 Consumers Energy Company [Member]	Sep. 30, 2012 Internal Revenue Service (IRS) [Member]	May 31, 2012 Internal Revenue Service (IRS) [Member]
U.S. federal income tax rate			35.00%	35.00%			35.00%	35.00%
MCIT law change, net of federal benefit				(5.90%)
State and local income taxes, net of federal benefit			4.70%	3.40%			5.00%	3.10%
Other, net				(1.40%)			(0.20%)	(1.40%)
Effective income tax rate			39.70%	31.10%			39.80%	36.70%
Net operating loss carryforward										$ 45
Net income	$ (149)	$ (140)	$ (317)	$ (376)	$ (163)	$ (155)	$ (361)	$ (400)	$ 1