XML 34 R31.htm IDEA: XBRL DOCUMENT
v2.4.1.9

Regulatory Matters (Narrative) (Details) (Consumers Energy Company [Member], USD $) In Millions, unless otherwise specified | 1 Months Ended |
--- | --- | ---
Jan. 31, 2015 | Jul. 31, 2014 | Dec. 31, 2014
Consumers Energy Company [Member] |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |
Annual rate increase requested |  | $ 88 us-gaap_PublicUtilitiesRequestedRateIncreaseDecreaseAmount / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |
Annual rate increase authorized | 45 us-gaap_PublicUtilitiesApprovedRateIncreaseDecreaseAmount / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |  |
Rate of return on equity authorized | 10.30%us-gaap_PublicUtilitiesApprovedReturnOnEquityPercentage / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |  |
Energy optimization incentive requested for exceeding savings targets |  |  | $ 17 cms_RequestedEnergyOptimizationIncentive / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember

X
- Definition Energy optimization incentive requested for achieving electric and gas savings targets. + References No definition available. + Details
Name: | cms_RequestedEnergyOptimizationIncentive
Namespace Prefix: | cms_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount of public utility's approved rate increase (decrease) by regulatory agency. + References No definition available. + Details
Name: | us-gaap_PublicUtilitiesApprovedRateIncreaseDecreaseAmount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Percentage of public utility's approved return on equity. + References No definition available. + Details
Name: | us-gaap_PublicUtilitiesApprovedReturnOnEquityPercentage
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_PublicUtilitiesGeneralDisclosuresLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of public utility's requested rate increase (decrease) with regulatory agency. + References No definition available. + Details
Name: | us-gaap_PublicUtilitiesRequestedRateIncreaseDecreaseAmount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration