Retirement Benefits (Schedule Of Expected Benefit Payments) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefit Payments, 2015	$ 134
Benefit Payments, 2016	141
Benefit Payments, 2017	147
Benefit Payments, 2018	152
Benefit Payments, 2019	156
Benefit Payments, 2020-2024	810
Pension Plan [Member] \| Consumers Energy Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefit Payments, 2015	131
Benefit Payments, 2016	137
Benefit Payments, 2017	143
Benefit Payments, 2018	148
Benefit Payments, 2019	152
Benefit Payments, 2020-2024	789
DB SERP [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefit Payments, 2015	8
Benefit Payments, 2016	8
Benefit Payments, 2017	8
Benefit Payments, 2018	8
Benefit Payments, 2019	9
Benefit Payments, 2020-2024	50
DB SERP [Member] \| Consumers Energy Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefit Payments, 2015	5
Benefit Payments, 2016	5
Benefit Payments, 2017	5
Benefit Payments, 2018	5
Benefit Payments, 2019	5
Benefit Payments, 2020-2024	30
OPEB [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefit Payments, 2015	56
Benefit Payments, 2016	58
Benefit Payments, 2017	61
Benefit Payments, 2018	64
Benefit Payments, 2019	67
Benefit Payments, 2020-2024	367
OPEB [Member] \| Consumers Energy Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefit Payments, 2015	53
Benefit Payments, 2016	56
Benefit Payments, 2017	59
Benefit Payments, 2018	62
Benefit Payments, 2019	64
Benefit Payments, 2020-2024	$ 352

Name:	us-gaap_DefinedBenefitPlanDisclosureLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Amount of benefits from a defined benefit plan expected to be paid in the five fiscal years after the fifth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ 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 (f)

-URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920

+ Details

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

- Definition

Amount of benefits from a defined benefit plan expected to be paid in the next fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

+ Details

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

- Definition

Amount of benefits from a defined benefit plan expected to be paid in the fifth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

+ Details

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

- Definition

Amount of benefits from a defined benefit plan expected to be paid in the fourth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

+ Details

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

- Definition

Amount of benefits from a defined benefit plan expected to be paid in the third fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

+ Details

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

- Definition

Amount of benefits from a defined benefit plan expected to be paid in the second fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

+ Details

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

- Details

Name:	us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis=us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis=us-gaap_PensionPlansDefinedBenefitMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis=us-gaap_SupplementalEmployeeRetirementPlanDefinedBenefitMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: