Financings and Capitalization (Narrative) (Details) (Consumers Energy Company [Member], USD $)	12 Months Ended
	Dec. 31, 2011
Short-term Securities [Member]
Maximum limitation on outstanding securities	$ 1,000,000,000
Remaining availability	700,000,000
Expiration date of authorizations	June 30, 2012
Long-term Securities [Member]
Maximum limitation on outstanding securities	2,500,000,000
Remaining availability	$ 1,400,000,000
Expiration date of authorizations	June 30 2012