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Retirement Benefits (Narrative) (Details) (OPEB [Member], USD $) In Millions, unless otherwise specified | 9 Months Ended
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Sep. 30, 2014
Defined Benefit Plan Disclosure [Line Items] |
Plan contributions, remainder of fiscal year | $ 25
Estimated future employer contributions | 29
Consumers Energy Company [Member] |
Defined Benefit Plan Disclosure [Line Items] |
Plan contributions, remainder of fiscal year | 25
Estimated future employer contributions | $ 29

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- Definition Amount of employer's best estimate of contributions expected to be paid to the plan in the current remaining fiscal period. + References No definition available. + Details
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- Definition Amount of employer's best estimate of contributions expected to be paid to the plan during the next fiscal year beginning after the date of the latest statement of financial position. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (g) -URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920 + Details
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