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