Leases (Schedule of Future Minimum Lease Payments for Leases) (Details) (Consumers Energy Company [Member], USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011 years		Dec. 31, 2010	Dec. 31, 2009
Consumers Energy Company [Member]
Capital Leases Future Minimum Payments Due Current	$ 20
Capital Leases Future Minimum Payments Due In Two Years	13
Capital Leases Future Minimum Payments Due In Three Years	11
Capital Leases Future Minimum Payments Due In Four Years	12
Capital Leases Future Minimum Payments Due In Five Years	8
Capital Leases Future Minimum Payments Due Thereafter	39
Capital Leases Future Minimum Payments Due	103
Capital Leases Future Minimum Payments Interest Included In Payments	46
Capital Leases Future Minimum Payments Present Value Of Net Minimum Payments, Total	57
Capital Leases Future Minimum Payments Present Value Of Net Minimum Payments, Current Portion	11
Capital Leases Future Minimum Payments Present Value Of Net Minimum Payments, Non Current Portion	46
Finance Leases Future Minimum Payments Due Current	20	[1]
Finance Leases Future Minimum Payments Due In Two Years	20	[1]
Finance Leases Future Minimum Payments Due In Three Years	19	[1]
Finance Leases Future Minimum Payments Due In Four Years	18	[1]
Finance Leases Future Minimum Payments Due In Five Years	17	[1]
Finance Leases Future Minimum Payments Due Thereafter	79	[1]
Finance Leases Future Minimum Payments Due	173	[1]
Finance Leases Future Minimum Payments Interest Included In Payments	39	[1]
Finance Leases Future Minimum Payments Present Value Of Net Minimum Payments	134	[1]
Finance Leases Future Minimum Payments Present Value Of Net Minimum Payments, Current Portion	13	[1]
Finance Leases Future Minimum Payments Present Value Of Net Minimum Payments, Non Current Portion	121	[1]
Operating Leases Future Minimum Payments Due Current	27
Operating Leases Future Minimum Payments Due In Two Years	24
Operating Leases Future Minimum Payments Due In Three Years	22
Operating Leases Future Minimum Payments Due In Four Years	22
Operating Leases Future Minimum Payments Due In Five Years	17
Operating Leases Future Minimum Payments Due Thereafter	68
Operating Leases Future Minimum Payments Due	180
Finance Lease Term	15
Finance Leases Lessee Balance Sheet Assets Amortization And Interest Charges	$ 21		$ 22	$ 23

[1] In 2007, Consumers sold Palisades to Entergy and entered into a 15-year PPA to buy all of the capacity and energy then capable of being produced by Palisades. Consumers has continuing involvement with Palisades through security provided to Entergy for Consumers' PPA obligation and other arrangements. Because of these ongoing arrangements, Consumers accounted for the transaction as a financing of Palisades and not a sale. Accordingly, no gain on the sale of Palisades was recognized on the consolidated statements of income. Consumers accounted for the remaining non-real-estate assets and liabilities associated with the transaction as a sale. Palisades remains on Consumers' consolidated balance sheets and Consumers continues to depreciate it. Consumers recorded the related proceeds as a finance obligation with payments recorded to interest expense and the finance obligation based on the amortization of the obligation over the life of the Palisades PPA. The value of the finance obligation was determined based on an allocation of the transaction proceeds to the fair values of the net assets sold and fair value of the plant asset under the financing. Total amortization and interest charges under the financing were $21 million, $22 million, and $23 million respectively, for the years ended December 31, 2011, 2010, and 2009.