Financings And Capitalization (Revolving Credit Facilities) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014
Revolving Credit Facilities December 20, 2018 [Member]
Line of Credit Facility [Line Items]
Expiration Date	Dec. 20, 2018	[1]
Amount of Facility	$ 550	[1]
Amount Borrowed		[1]
Letters of Credit Outstanding	3	[1]
Amount Available	547	[1]
Revolving Credit Facilities December 20, 2018 [Member] | Consumers Energy Company [Member]
Line of Credit Facility [Line Items]
Expiration Date	Dec. 20, 2018	[2]
Amount of Facility	650	[2]
Amount Borrowed		[2]
Letters of Credit Outstanding	35	[2]
Amount Available	615	[2]
Revolving Credit Facilities May 9, 2018 [Member] | Consumers Energy Company [Member]
Line of Credit Facility [Line Items]
Expiration Date	May 09, 2018	[2]
Amount of Facility	30	[2]
Amount Borrowed		[2]
Letters of Credit Outstanding	$ 30	[2]

[1] Obligations under this facility are secured by Consumers common stock.

[2] Obligations under this facility are secured by FMBs of Consumers.