Income Taxes (Details)	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
U.S. federal income tax rate	35.00%	35.00%
State and local income taxes, net of federal effect	4.90%	4.90%
Accelerated flow-through of regulatory tax benefits	(5.40%)
Other, net	(0.50%)	(0.20%)
Effective tax rate	34.00%	39.70%
Consumers Energy Company [Member]
U.S. federal income tax rate	35.00%	35.00%
State and local income taxes, net of federal effect	4.90%	4.80%
Accelerated flow-through of regulatory tax benefits	(4.80%)
Other, net	(0.70%)	(0.90%)
Effective tax rate	34.40%	38.90%