Retirement Benefits (Schedule Of Expected Benefit Payments) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2013
Pension [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefit Payments, 2014	$ 119
Benefit Payments, 2015	127
Benefit Payments, 2016	134
Benefit Payments, 2017	139
Benefit Payments, 2018	144
Benefit Payments, 2019-2023	760
Pension [Member] | Consumers Energy Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefit Payments, 2014	116
Benefit Payments, 2015	124
Benefit Payments, 2016	131
Benefit Payments, 2017	136
Benefit Payments, 2018	140
Benefit Payments, 2019-2023	740
DB SERP [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefit Payments, 2014	8
Benefit Payments, 2015	8
Benefit Payments, 2016	8
Benefit Payments, 2017	8
Benefit Payments, 2018	8
Benefit Payments, 2019-2023	48
DB SERP [Member] | Consumers Energy Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefit Payments, 2014	4
Benefit Payments, 2015	5
Benefit Payments, 2016	5
Benefit Payments, 2017	5
Benefit Payments, 2018	5
Benefit Payments, 2019-2023	27
OPEB [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefit Payments, 2014	58	[1]
Benefit Payments, 2015	59	[1]
Benefit Payments, 2016	61	[1]
Benefit Payments, 2017	64	[1]
Benefit Payments, 2018	66	[1]
Benefit Payments, 2019-2023	364	[1]
Subsidy to be received, 2014	6
OPEB [Member] | Consumers Energy Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefit Payments, 2014	56	[1]
Benefit Payments, 2015	57	[1]
Benefit Payments, 2016	59	[1]
Benefit Payments, 2017	61	[1]
Benefit Payments, 2018	64	[1]
Benefit Payments, 2019-2023	349	[1]
Subsidy to be received, 2014	$ 5

[1] CMS Energy’s and Consumers’ OPEB benefit payments are net of employee contributions and expected Medicare Part D subsidy payments for 2014. CMS Energy and Consumers plan to change the Medicare drug program provided through the OPEB Plan from an employer-sponsored drug plan to an EGWP to begin on January 1, 2015; therefore, no Medicare Part D subsidy is expected after 2014. For CMS Energy, subsidies to be received are estimated to be $6 million for 2014. For Consumers, subsidies to be received are estimated to be $5 million for 2014.