Income Taxes (Details)	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
U.S. federal income tax rate	35.00%	35.00%
State and local income taxes, net of federal effect	4.80%	4.90%
Accelerated flow-through of regulatory tax benefits	(4.90%)	(5.40%)
Other, net	(1.80%)	(0.50%)
Effective tax rate	33.10%	34.00%
Consumers Energy Company [Member]
U.S. federal income tax rate	35.00%	35.00%
State and local income taxes, net of federal effect	4.70%	4.90%
Accelerated flow-through of regulatory tax benefits	(4.40%)	(4.80%)
Other, net	(1.50%)	(0.70%)
Effective tax rate	33.80%	34.40%