Leases (Schedule of Future Minimum Lease Payments for Leases) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Leases [Line Items]
Capital and Financing Leases, Non-current portion	$ 138	$ 153
Operating Leases, 2014	26
Operating Leases, 2015	25
Operating Leases, 2016	20
Operating Leases, 2017	20
Operating Leases, 2018	17
Operating Leases, 2019 and thereafter	56
Operating Leases, Total minimum lease payments	164
Capital Leases [Member]
Leases [Line Items]
Capital and Financing Leases, 2014	14
Capital and Financing Leases, 2015	14
Capital and Financing Leases, 2016	11
Capital and Financing Leases, 2017	10
Capital and Financing Leases, 2018	10
Capital and Financing Leases, 2019 and thereafter	31
Capital and Financing Leases, Total minimum lease payments	90
Capital and Financing Leases, Less imputed interest	39
Capital and Financing Leases, Present value of net minimum lease payments	51
Capital and Financing Leases, Less current portion	8
Capital and Financing Leases, Non-current portion	43
Financing Leases [Member]
Leases [Line Items]
Capital and Financing Leases, 2014	19
Capital and Financing Leases, 2015	18
Capital and Financing Leases, 2016	17
Capital and Financing Leases, 2017	17
Capital and Financing Leases, 2018	16
Capital and Financing Leases, 2019 and thereafter	46
Capital and Financing Leases, Total minimum lease payments	133
Capital and Financing Leases, Less imputed interest	25
Capital and Financing Leases, Present value of net minimum lease payments	108
Capital and Financing Leases, Less current portion	13
Capital and Financing Leases, Non-current portion	95
Consumers Energy Company [Member]
Leases [Line Items]
Capital and Financing Leases, Non-current portion	138	153
Operating Leases, 2014	26
Operating Leases, 2015	25
Operating Leases, 2016	20
Operating Leases, 2017	20
Operating Leases, 2018	17
Operating Leases, 2019 and thereafter	56
Operating Leases, Total minimum lease payments	164
Consumers Energy Company [Member] | Capital Leases [Member]
Leases [Line Items]
Capital and Financing Leases, 2014	14
Capital and Financing Leases, 2015	14
Capital and Financing Leases, 2016	11
Capital and Financing Leases, 2017	10
Capital and Financing Leases, 2018	10
Capital and Financing Leases, 2019 and thereafter	31
Capital and Financing Leases, Total minimum lease payments	90
Capital and Financing Leases, Less imputed interest	39
Capital and Financing Leases, Present value of net minimum lease payments	51
Capital and Financing Leases, Less current portion	8
Capital and Financing Leases, Non-current portion	43
Consumers Energy Company [Member] | Financing Leases [Member]
Leases [Line Items]
Capital and Financing Leases, 2014	19
Capital and Financing Leases, 2015	18
Capital and Financing Leases, 2016	17
Capital and Financing Leases, 2017	17
Capital and Financing Leases, 2018	16
Capital and Financing Leases, 2019 and thereafter	46
Capital and Financing Leases, Total minimum lease payments	133
Capital and Financing Leases, Less imputed interest	25
Capital and Financing Leases, Present value of net minimum lease payments	108
Capital and Financing Leases, Less current portion	13
Capital and Financing Leases, Non-current portion	$ 95