Financings And Capitalization (Revolving Credit Facilities) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013
Revolving Credit Facilities December 21, 2017 [Member]
Expiration Date	Dec. 21, 2017	[1]
Amount of Facility	$ 550	[1]
Amount Borrowed		[1]
Letters of Credit Outstanding	2	[1]
Amount Available	548	[1]
Revolving Credit Facilities December 21, 2017 [Member] | Consumers Energy Company [Member]
Expiration Date	Dec. 21, 2017	[2]
Amount of Facility	500	[2]
Amount Borrowed		[2]
Letters of Credit Outstanding	2	[2]
Amount Available	498	[2]
Revolving Credit Facilities April 18, 2017 [Member] | Consumers Energy Company [Member]
Expiration Date	Apr. 18, 2017	[2]
Amount of Facility	150	[2]
Amount Borrowed		[2]
Amount Available	150	[2]
Revolving Credit Facilities September 9, 2014 [Member] | Consumers Energy Company [Member]
Expiration Date	Sep. 09, 2014	[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.