Regulatory Matters (Narrative) (Details) (Consumers Energy Company [Member], USD $) In Millions, unless otherwise specified	1 Months Ended
	Jan. 31, 2015	Jul. 31, 2014	Dec. 31, 2014
Consumers Energy Company [Member]
Public Utilities, General Disclosures [Line Items]
Annual rate increase requested		$ 88
Annual rate increase authorized	45
Rate of return on equity authorized	10.30%
Energy optimization incentive requested for exceeding savings targets			$ 17