Regulatory Matters (Components of the Increase in Revenue for Electric Rate Increase) (Details) - Electric Rate Case [Member] - Consumers Energy Company [Member] $ in Millions	1 Months Ended
	Dec. 31, 2014 USD ($)
Public Utilities, General Disclosures [Line Items]
Investment in rate base	$ 185
Addition of natural gas-fueled electric generation plant	35
Operating and maintenance costs	26
Cost of capital	21
Working capital	6
Cost-reduction initiatives	(80)
Gross margin	(30)
Annual rate increase requested	$ 163