Regulatory Matters (Schedule of the Components of the Annual Rate Increase Authorized and Requested) (Details) (2010 Gas Rate Case [Member], Consumers Energy Company [Member], USD $) In Millions, unless otherwise specified	1 Months Ended
	May 31, 2011	Aug. 31, 2010
Annual Rate Increase Authorized by the MPSC	$ 31
Annual Rate Increase Requested by Consumers		55
Difference Between Annual Rate Increase Authorized and Annual Rate Increase Requested	(24)
Investment in Rate Base [Member]
Annual Rate Increase Authorized by the MPSC	29
Annual Rate Increase Requested by Consumers		30
Difference Between Annual Rate Increase Authorized and Annual Rate Increase Requested	(1)
Impact Of Sales Declines [Member]
Annual Rate Increase Authorized by the MPSC	15
Annual Rate Increase Requested by Consumers		4
Difference Between Annual Rate Increase Authorized and Annual Rate Increase Requested	11
Operating And Maintenance Costs [Member]
Annual Rate Increase Authorized by the MPSC	2
Annual Rate Increase Requested by Consumers		16
Difference Between Annual Rate Increase Authorized and Annual Rate Increase Requested	(14)
Cost Of Capital [Member]
Annual Rate Increase Authorized by the MPSC	(15)
Annual Rate Increase Requested by Consumers		5
Difference Between Annual Rate Increase Authorized and Annual Rate Increase Requested	$ (20)