Retirement Benefits (Schedule Of SERP Trust Assets, ABO And Contributions) (Details) (DB SERP [Member], USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2013	Dec. 31, 2012
Defined Benefit Plan Disclosure [Line Items]
ABO	$ 122	$ 130
Contributions	16	13
Consumers Energy Company [Member]
Defined Benefit Plan Disclosure [Line Items]
ABO	82	86
Contributions	13	9
DB SERP Trust Assets [Member]
Defined Benefit Plan Disclosure [Line Items]
Trust assets	136	128
DB SERP Trust Assets [Member] \| Consumers Energy Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Trust assets	$ 96	$ 87

For defined benefit pension plans, the actuarial present value of benefits (whether vested or nonvested) attributed by the pension benefit formula to employee service rendered before a specified date and based on employee service and compensation (if applicable) before that date. The accumulated benefit obligation differs from the projected benefit obligation in that it includes no assumption about future compensation levels. For plans with flat-benefit or nonpay-related pension benefit formulas, the accumulated benefit obligation and the projected benefit obligation are the same.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Accumulated Benefit Obligation

-URI http://asc.fasb.org/extlink&oid=6503844

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (e)

-URI http://asc.fasb.org/extlink&oid=28361610&loc=d3e1928-114920

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant