Leases (Schedule of Future Minimum Lease Payments for Leases) (Details) - USD ($) $ in Millions		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Leases [Line Items]
Capital and Financing Leases, Non-current portion		$ 118	$ 123
Consumers Energy Company [Member]
Leases [Line Items]
Capital and Financing Leases, Non-current portion		118	123
Operating Leases, 2016		20
Operating Leases, 2017		19
Operating Leases, 2018		16
Operating Leases, 2019		10
Operating Leases, 2020		10
Operating Leases, 2021 and thereafter		29
Operating Leases, Total minimum lease payments		104
Finance Leases Lessee Balance Sheet Assets Amortization And Interest Charges		18	$ 19	$ 20
Consumers Energy Company [Member] | Capital Leases [Member]
Leases [Line Items]
Capital and Financing Leases, 2016		14
Capital and Financing Leases, 2017		14
Capital and Financing Leases, 2018		13
Capital and Financing Leases, 2019		13
Capital and Financing Leases, 2020		11
Capital and Financing Leases, 2021 and thereafter		36
Capital and Financing Leases, Total minimum lease payments		101
Capital and Financing Leases, Less imputed interest		43
Capital and Financing Leases, Present value of net minimum lease payments		58
Capital and Financing Leases, Less current portion		9
Capital and Financing Leases, Non-current portion		49
Consumers Energy Company [Member] | Financing Leases [Member]
Leases [Line Items]
Capital and Financing Leases, 2016	[1]	17
Capital and Financing Leases, 2017	[1]	17
Capital and Financing Leases, 2018	[1]	16
Capital and Financing Leases, 2019	[1]	15
Capital and Financing Leases, 2020	[1]	14
Capital and Financing Leases, 2021 and thereafter	[1]	17
Capital and Financing Leases, Total minimum lease payments	[1]	96
Capital and Financing Leases, Less imputed interest	[1]	14
Capital and Financing Leases, Present value of net minimum lease payments	[1]	82
Capital and Financing Leases, Less current portion	[1]	13
Capital and Financing Leases, Non-current portion	[1]	$ 69

[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 financing obligation with payments recorded to interest expense and the financing obligation based on the amortization of the obligation over the life of the Palisades PPA. The value of the financing 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 $18 million for the year ended December 31, 2015, $19 million for the year ended December 31, 2014, and $20 million for the year ended December 31, 2013.