Plant, Property, and Equipment (Schedule of Capital Leased Asssets) (Details) (Consumers Energy Company [Member], USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010
Consumers Energy Company [Member]
Balance at beginning of period	$ 278	$ 306
Capital Leased Assets, Gross, Additions	4	15
Capital Leased Assets, Gross, Disposals and Transfers	(2)	(43)
Balance at end of period	280	278
Capital Leases, Lessee Balance Sheet, Assets by Major Class, Accumulated Depreciation	$ 87	$ 65