Regulatory Matters (Schedule of Components of the Increase in Gas Revenue) (Details) (2011 Gas Rate Case [Member], Consumers Energy Company [Member], USD $) In Millions	Sep. 30, 2011
Annual Rate Increase Requested by Consumers	$ 49
Investment in Rate Base [Member]
Annual Rate Increase Requested by Consumers	22
Impact of Reduced Funding for Customers Assistance Programs [Member]
Annual Rate Increase Requested by Consumers	19	[1]
Cost Of Capital [Member]
Annual Rate Increase Requested by Consumers	10
Impact Of Sales Declines [Member]
Annual Rate Increase Requested by Consumers	2
Reduced Operating And Maintenance Costs [Member]
Annual Rate Increase Requested by Consumers	$ (4)

[1] 1 Consumers projects gas uncollectible expense to increase by $19 million in 2012 due to an anticipated reduction in federal and state funding for customer assistance programs. Due to the uncertainty surrounding federal and state funding for such programs and the resulting impact on uncollectible expense, Consumers also requested that the MPSC approve an uncollectible expense true-up mechanism.