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, 2014	Dec. 31, 2013
Consumers Energy Company [Member]
Balance at beginning of period	$ 291	$ 285
Capital Leased Assets, Gross, Additions	7	12
Capital Leased Assets, Gross, Disposals and Transfers	(3)	(6)
Balance at end of period	295	291
Capital Leases, Lessee Balance Sheet, Assets by Major Class, Accumulated Depreciation	$ 143	$ 124