Income Taxes (Narrative) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014
Income Tax Benefits [Line Items]
IRS audit, adjustments to income tax expense	$ 0
Consumers Energy Company [Member]
Income Tax Benefits [Line Items]
Reduction of income tax expense	16
IRS audit, adjustments to income tax expense	0
Consumers Energy Company [Member] | Electric Utility [Member]
Income Tax Benefits [Line Items]
Income tax benefits, to be returned to customers	211
Tax benefit, distribution to customers, term	5 years
Consumers Energy Company [Member] | Gas Utility [Member]
Income Tax Benefits [Line Items]
Income tax benefits, to be returned to customers	$ 264
Tax benefit, distribution to customers, term	12 years