Leases (Schedule of Future Minimum Lease Payments for Leases) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013	Dec. 31, 2012
Leases [Line Items]
Capital and Financing Leases, Non-current portion	$ 123		$ 138
Finance Leases Lessee Balance Sheet Assets Amortization And Interest Charges	19		20	20
Consumers Energy Company [Member]
Leases [Line Items]
Capital and Financing Leases, Non-current portion	123		138
Operating Leases, 2015	25
Operating Leases, 2016	19
Operating Leases, 2017	19
Operating Leases, 2018	16
Operating Leases, 2019	10
Operating Leases, 2020 and thereafter	40
Operating Leases, Total minimum lease payments	129
Finance Leases Lessee Balance Sheet Assets Amortization And Interest Charges	19		20	20
Consumers Energy Company [Member] | Capital Leases [Member]
Leases [Line Items]
Capital and Financing Leases, 2015	15
Capital and Financing Leases, 2016	12
Capital and Financing Leases, 2017	11
Capital and Financing Leases, 2018	10
Capital and Financing Leases, 2019	11
Capital and Financing Leases, 2020 and thereafter	25
Capital and Financing Leases, Total minimum lease payments	84
Capital and Financing Leases, Less imputed interest	35
Capital and Financing Leases, Present value of net minimum lease payments	49
Capital and Financing Leases, Less current portion	8
Capital and Financing Leases, Non-current portion	41
Consumers Energy Company [Member] | Financing Leases [Member]
Leases [Line Items]
Capital and Financing Leases, 2015	18	[1]
Capital and Financing Leases, 2016	17	[1]
Capital and Financing Leases, 2017	17	[1]
Capital and Financing Leases, 2018	16	[1]
Capital and Financing Leases, 2019	15	[1]
Capital and Financing Leases, 2020 and thereafter	31	[1]
Capital and Financing Leases, Total minimum lease payments	114	[1]
Capital and Financing Leases, Less imputed interest	19	[1]
Capital and Financing Leases, Present value of net minimum lease payments	95	[1]
Capital and Financing Leases, Less current portion	13	[1]
Capital and Financing Leases, Non-current portion	$ 82	[1]

[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 $19 million for the year ended December 31, 2014 and $20 million for each of the years ended December 31, 2013 and December 31, 2012.