Financings And Capitalization (Revolving Credit Facilities) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013
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	2	[1]
Amount Available	548	[1]
Average borrowings	4
Weighted average interest rate	1.67%
LIBOR plus	1.50%
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]
Amount Available	650	[2]
Revolving Credit Facilities September 9, 2014 [Member] | Consumers Energy Company [Member]
Line of Credit Facility [Line Items]
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. CMS Energy’s average borrowings during the year ended December 31, 2013 were $4 million, with a weighted-average annual interest rate of 1.67 percent, representing LIBOR plus 1.50 percent.

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