Income Taxes (Details)	6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013
U.S. federal income tax rate	35.00%	35.00%
State and local income taxes, net of federal effect	5.00%	4.90%
Accelerated flow-through of regulatory tax benefits	(5.40%)
Other, net	(0.60%)
Effective tax rate	34.00%	39.90%
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	(4.50%)
Other, net	(0.60%)	(0.40%)
Effective tax rate	34.80%	39.40%