Retirement Benefits (Schedule Of Pooled Funds Components) (Details)	Dec. 31, 2015	Dec. 31, 2014
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
U.S. equity securities	62.00%	64.00%
Foreign equity securities	18.00%	16.00%
U.S. fixed-income securities	11.00%	9.00%
Foreign fixed-income securities	6.00%	6.00%
Alternative investments	3.00%	5.00%
Pension Plan [Member] \| Consumers Energy Company [Member]
Defined Benefit Plan Disclosure [Line Items]
U.S. equity securities	62.00%	64.00%
Foreign equity securities	18.00%	16.00%
U.S. fixed-income securities	11.00%	9.00%
Foreign fixed-income securities	6.00%	6.00%
Alternative investments	3.00%	5.00%
OPEB [Member]
Defined Benefit Plan Disclosure [Line Items]
U.S. equity securities	58.00%	62.00%
Foreign equity securities	13.00%	12.00%
U.S. fixed-income securities	22.00%	18.00%
Foreign fixed-income securities	5.00%	5.00%
Alternative investments	2.00%	3.00%
OPEB [Member] \| Consumers Energy Company [Member]
Defined Benefit Plan Disclosure [Line Items]
U.S. equity securities	58.00%	62.00%
Foreign equity securities	13.00%	12.00%
U.S. fixed-income securities	22.00%	18.00%
Foreign fixed-income securities	5.00%	5.00%
Alternative investments	2.00%	3.00%

Alternative investments included in the Pooled funds category of the Plan trust assets.

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Foreign equity securities included in the Pooled funds category of the Plan trust assets.

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Foreign fixed-income securities included in the Pooled funds category of the Plan trust assets.

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U.S. equity securities included in the Pooled funds category of the Plan trust assets.

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U.S. fixed-income securities included in the Pooled funds category of the Plan trust assets.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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