XML 71 R62.htm IDEA: XBRL DOCUMENT
v2.4.1.9

Financings and Capitalization (Summary of Long-Term Debt Outstanding) (Details) (USD $) | 12 Months Ended |
--- | --- | ---
Dec. 31, 2014 | Dec. 31, 2013
Debt Instrument [Line Items] |  |  |  |
Principal amounts outstanding | $ 8,547,000,000 us-gaap_DebtInstrumentCarryingAmount |  | $ 7,654,000,000 us-gaap_DebtInstrumentCarryingAmount |
Current portion of long-term debt | (519,000,000)us-gaap_LongTermDebtCurrent |  | (541,000,000)us-gaap_LongTermDebtCurrent |
Net unamortized discount | (12,000,000)us-gaap_DebtInstrumentUnamortizedDiscountPremiumNet |  | (12,000,000)us-gaap_DebtInstrumentUnamortizedDiscountPremiumNet |
Total long-term debt | 8,016,000,000 us-gaap_LongTermDebtNoncurrent |  | 7,101,000,000 us-gaap_LongTermDebtNoncurrent |
Debt retirement, principal | 707,000,000 us-gaap_RepaymentsOfDebt |  |  |
Consumers Energy Company [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Principal amounts outstanding | 5,283,000,000 us-gaap_DebtInstrumentCarryingAmount / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |  | 4,625,000,000 us-gaap_DebtInstrumentCarryingAmount / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |
Current portion of long-term debt | (124,000,000)us-gaap_LongTermDebtCurrent / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |  | (43,000,000)us-gaap_LongTermDebtCurrent / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |
Net unamortized discount | (5,000,000)us-gaap_DebtInstrumentUnamortizedDiscountPremiumNet / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |  | (3,000,000)us-gaap_DebtInstrumentUnamortizedDiscountPremiumNet / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |
Total long-term debt | 5,154,000,000 us-gaap_LongTermDebtNoncurrent / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |  | 4,579,000,000 us-gaap_LongTermDebtNoncurrent / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |
Debt retirement, principal | 177,000,000 us-gaap_RepaymentsOfDebt / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |  |  |
CMS Energy [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Principal amounts outstanding | 2,380,000,000 us-gaap_DebtInstrumentCarryingAmount / dei_LegalEntityAxis = us-gaap_ParentCompanyMember |  | 2,377,000,000 us-gaap_DebtInstrumentCarryingAmount / dei_LegalEntityAxis = us-gaap_ParentCompanyMember |
Net unamortized discount | (7,000,000)us-gaap_DebtInstrumentUnamortizedDiscountPremiumNet / dei_LegalEntityAxis = us-gaap_ParentCompanyMember |  | (9,000,000)us-gaap_DebtInstrumentUnamortizedDiscountPremiumNet / dei_LegalEntityAxis = us-gaap_ParentCompanyMember |
Total long-term debt | 2,380,000,000 us-gaap_LongTermDebtNoncurrent / dei_LegalEntityAxis = us-gaap_ParentCompanyMember |  | 2,205,000,000 us-gaap_LongTermDebtNoncurrent / dei_LegalEntityAxis = us-gaap_ParentCompanyMember |
Debt retirement, principal | 530,000,000 us-gaap_RepaymentsOfDebt / dei_LegalEntityAxis = us-gaap_ParentCompanyMember |  |  |
Senior Notes 6.875% Due December 2015 [Member] | CMS Energy [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Interest rate | 6.875%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_DebtInstrumentAxis = cms_SeniorNotesThreeMember / dei_LegalEntityAxis = us-gaap_ParentCompanyMember | [1] |  |
Debt retirement, principal | 125,000,000 us-gaap_RepaymentsOfDebt / us-gaap_DebtInstrumentAxis = cms_SeniorNotesThreeMember / dei_LegalEntityAxis = us-gaap_ParentCompanyMember | [1] |  |
Senior Notes 4.250% Due 2015 [Member] | CMS Energy [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Interest rate | 4.25%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_DebtInstrumentAxis = cms_SeniorNotesFiveMember / dei_LegalEntityAxis = us-gaap_ParentCompanyMember | [2] |  |
Debt retirement, principal | 250,000,000 us-gaap_RepaymentsOfDebt / us-gaap_DebtInstrumentAxis = cms_SeniorNotesFiveMember / dei_LegalEntityAxis = us-gaap_ParentCompanyMember | [2] |  |
Senior Notes 3.875% Due March 2024 [Member] | CMS Energy [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Interest rate | 3.875%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_DebtInstrumentAxis = cms_SeniorNotesOneMember / dei_LegalEntityAxis = us-gaap_ParentCompanyMember |  |  |
Senior Notes 5.500% Due June 2029 [Member] | CMS Energy [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Interest rate | 5.50%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_DebtInstrumentAxis = cms_SeniorNotesFourMember / dei_LegalEntityAxis = us-gaap_ParentCompanyMember |  |  |
Debt retirement, principal | 155,000,000 us-gaap_RepaymentsOfDebt / us-gaap_DebtInstrumentAxis = cms_SeniorNotesFourMember / dei_LegalEntityAxis = us-gaap_ParentCompanyMember |  |  |
Senior Notes 4.875% Due March 2044 [Member] | CMS Energy [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Interest rate | 4.875%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_DebtInstrumentAxis = cms_SeniorNotesTwoMember / dei_LegalEntityAxis = us-gaap_ParentCompanyMember |  |  |
Term Loan Facility Due 2017 [Member] | CMS Energy [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Maturity Date | 2017 |  |  |
Principal amounts outstanding | 180,000,000 us-gaap_DebtInstrumentCarryingAmount / us-gaap_DebtInstrumentAxis = cms_ShortTermLoanFacilityOneMember / dei_LegalEntityAxis = us-gaap_ParentCompanyMember |  | 180,000,000 us-gaap_DebtInstrumentCarryingAmount / us-gaap_DebtInstrumentAxis = cms_ShortTermLoanFacilityOneMember / dei_LegalEntityAxis = us-gaap_ParentCompanyMember |
Three-month LIBOR plus a spread | 1.25%us-gaap_DebtInstrumentBasisSpreadOnVariableRate1 / us-gaap_DebtInstrumentAxis = cms_ShortTermLoanFacilityOneMember / dei_LegalEntityAxis = us-gaap_ParentCompanyMember |  |  |
Interest rate at period end | 1.42%us-gaap_DebtInstrumentInterestRateEffectivePercentage / us-gaap_DebtInstrumentAxis = cms_ShortTermLoanFacilityOneMember / dei_LegalEntityAxis = us-gaap_ParentCompanyMember |  |  |
FMB's 5.500% Due August 2016 [Member] | Consumers Energy Company [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Interest rate | 5.50%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_DebtInstrumentAxis = cms_FirstMortgageBondsThreeMember / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |  |  |
Debt retirement, principal | 177,000,000 us-gaap_RepaymentsOfDebt / us-gaap_DebtInstrumentAxis = cms_FirstMortgageBondsThreeMember / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |  |  |
FMB's 3.125% Due August 2024 [Member] | Consumers Energy Company [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Interest rate | 3.125%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_DebtInstrumentAxis = cms_FirstMortgageBondsOneMember / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember | [3] |  |
Maturity Date | 2024 | [3] |  |
Principal amounts outstanding | 250,000,000 us-gaap_DebtInstrumentCarryingAmount / us-gaap_DebtInstrumentAxis = cms_FirstMortgageBondsOneMember / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember | [3] |  |
FMB's 4.350% Due August 2064 [Member] | Consumers Energy Company [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Interest rate | 4.35%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_DebtInstrumentAxis = cms_FirstMortgageBondsTwoMember / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |  |  |
Securitization Bonds 5.760% Due 2015 [Member] | Consumers Energy Company [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Interest rate | 5.76%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_DebtInstrumentAxis = cms_SecuritizationBondsFourMember / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |  |  |
Maturity Date | 2015 |  |  |
Principal amounts outstanding | 49,000,000 us-gaap_DebtInstrumentCarryingAmount / us-gaap_DebtInstrumentAxis = cms_SecuritizationBondsFourMember / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |  | 92,000,000 us-gaap_DebtInstrumentCarryingAmount / us-gaap_DebtInstrumentAxis = cms_SecuritizationBondsFourMember / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |
Securitization Bonds 2.597% Due 2015-2029 [Member] | Consumers Energy Company [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Interest rate | 2.597%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_DebtInstrumentAxis = cms_SecuritizationBondsFiveMember / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember | [4] |  |
Maturity Date | 2020-2029 |  |  |
Principal amounts outstanding | 378,000,000 us-gaap_DebtInstrumentCarryingAmount / us-gaap_DebtInstrumentAxis = cms_SecuritizationBondsFiveMember / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |  |  |
Securitization Bonds [Member] | Consumers Energy Company [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Principal amounts outstanding | 427,000,000 us-gaap_DebtInstrumentCarryingAmount / us-gaap_DebtInstrumentAxis = cms_SecuritizationBondsMember / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |  | 92,000,000 us-gaap_DebtInstrumentCarryingAmount / us-gaap_DebtInstrumentAxis = cms_SecuritizationBondsMember / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |
Securitization Bonds [Member] | Consumers Energy Company [Member] | Consumers Funding [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Weighted-average Interest Rate (%) | 5.76%us-gaap_LongtermDebtWeightedAverageInterestRate / us-gaap_DebtInstrumentAxis = cms_SecuritizationBondsMember / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = cms_ConsumersFundingMember |  |  |
Securitization Bonds [Member] | Consumers Energy Company [Member] | Consumers 2014 Securitization Funding [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Weighted-average Interest Rate (%) | 2.60%us-gaap_LongtermDebtWeightedAverageInterestRate / us-gaap_DebtInstrumentAxis = cms_SecuritizationBondsMember / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = cms_Consumers2014SecuritizationFundingMember |  |  |
Senior Notes 6.875% Due 2018 [Member] | Consumers Energy Company [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Interest rate | 6.875%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_DebtInstrumentAxis = cms_SeniorNotesTwelveMember / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |  |  |
Maturity Date | 2018 |  |  |
Principal amounts outstanding | 180,000,000 us-gaap_DebtInstrumentCarryingAmount / us-gaap_DebtInstrumentAxis = cms_SeniorNotesTwelveMember / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |  | 180,000,000 us-gaap_DebtInstrumentCarryingAmount / us-gaap_DebtInstrumentAxis = cms_SeniorNotesTwelveMember / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |
Tax-Exempt Pollution Control Revenue Bonds [Member] | Consumers Energy Company [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Maturity Date | 2018-2035 |  |  |
Principal amounts outstanding | 103,000,000 us-gaap_DebtInstrumentCarryingAmount / us-gaap_DebtInstrumentAxis = cms_PollutionControlRevenueBondsMember / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |  | 103,000,000 us-gaap_DebtInstrumentCarryingAmount / us-gaap_DebtInstrumentAxis = cms_PollutionControlRevenueBondsMember / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |
Senior Notes [Member] | CMS Energy [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Principal amounts outstanding | 2,200,000,000 us-gaap_DebtInstrumentCarryingAmount / dei_LegalEntityAxis = us-gaap_ParentCompanyMember / us-gaap_LongtermDebtTypeAxis = us-gaap_UnsecuredDebtMember |  | 2,197,000,000 us-gaap_DebtInstrumentCarryingAmount / dei_LegalEntityAxis = us-gaap_ParentCompanyMember / us-gaap_LongtermDebtTypeAxis = us-gaap_UnsecuredDebtMember |
Senior Notes [Member] | Senior Notes 6.875% Due December 2015 [Member] | CMS Energy [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Interest rate | 6.875%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_DebtInstrumentAxis = cms_SeniorNotesThreeMember / dei_LegalEntityAxis = us-gaap_ParentCompanyMember / us-gaap_LongtermDebtTypeAxis = us-gaap_UnsecuredDebtMember | [5] |  |
Maturity Date | 2015 |  |  |
Principal amounts outstanding |  |  | 125,000,000 us-gaap_DebtInstrumentCarryingAmount / us-gaap_DebtInstrumentAxis = cms_SeniorNotesThreeMember / dei_LegalEntityAxis = us-gaap_ParentCompanyMember / us-gaap_LongtermDebtTypeAxis = us-gaap_UnsecuredDebtMember |
Senior Notes [Member] | Senior Notes 4.250% Due 2015 [Member] | CMS Energy [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Interest rate | 4.25%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_DebtInstrumentAxis = cms_SeniorNotesFiveMember / dei_LegalEntityAxis = us-gaap_ParentCompanyMember / us-gaap_LongtermDebtTypeAxis = us-gaap_UnsecuredDebtMember | [6] |  |
Maturity Date | 2015 |  |  |
Principal amounts outstanding |  |  | 250,000,000 us-gaap_DebtInstrumentCarryingAmount / us-gaap_DebtInstrumentAxis = cms_SeniorNotesFiveMember / dei_LegalEntityAxis = us-gaap_ParentCompanyMember / us-gaap_LongtermDebtTypeAxis = us-gaap_UnsecuredDebtMember |
Senior Notes [Member] | Senior Notes 6.550% Due 2017 [Member] | CMS Energy [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Interest rate | 6.55%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_DebtInstrumentAxis = cms_SeniorNotesSixMember / dei_LegalEntityAxis = us-gaap_ParentCompanyMember / us-gaap_LongtermDebtTypeAxis = us-gaap_UnsecuredDebtMember |  |  |
Maturity Date | 2017 |  |  |
Principal amounts outstanding | 250,000,000 us-gaap_DebtInstrumentCarryingAmount / us-gaap_DebtInstrumentAxis = cms_SeniorNotesSixMember / dei_LegalEntityAxis = us-gaap_ParentCompanyMember / us-gaap_LongtermDebtTypeAxis = us-gaap_UnsecuredDebtMember |  | 250,000,000 us-gaap_DebtInstrumentCarryingAmount / us-gaap_DebtInstrumentAxis = cms_SeniorNotesSixMember / dei_LegalEntityAxis = us-gaap_ParentCompanyMember / us-gaap_LongtermDebtTypeAxis = us-gaap_UnsecuredDebtMember |
Senior Notes [Member] | Senior Notes 5.050% Due 2018 [Member] | CMS Energy [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Interest rate | 5.05%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_DebtInstrumentAxis = cms_SeniorNotesSevenMember / dei_LegalEntityAxis = us-gaap_ParentCompanyMember / us-gaap_LongtermDebtTypeAxis = us-gaap_UnsecuredDebtMember |  |  |
Maturity Date | 2018 |  |  |
Principal amounts outstanding | 250,000,000 us-gaap_DebtInstrumentCarryingAmount / us-gaap_DebtInstrumentAxis = cms_SeniorNotesSevenMember / dei_LegalEntityAxis = us-gaap_ParentCompanyMember / us-gaap_LongtermDebtTypeAxis = us-gaap_UnsecuredDebtMember |  | 250,000,000 us-gaap_DebtInstrumentCarryingAmount / us-gaap_DebtInstrumentAxis = cms_SeniorNotesSevenMember / dei_LegalEntityAxis = us-gaap_ParentCompanyMember / us-gaap_LongtermDebtTypeAxis = us-gaap_UnsecuredDebtMember |
Senior Notes [Member] | Senior Notes 8.750% Due 2019 [Member] | CMS Energy [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Interest rate | 8.75%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_DebtInstrumentAxis = cms_SeniorNotesEightMember / dei_LegalEntityAxis = us-gaap_ParentCompanyMember / us-gaap_LongtermDebtTypeAxis = us-gaap_UnsecuredDebtMember |  |  |
Maturity Date | 2019 |  |  |
Principal amounts outstanding | 300,000,000 us-gaap_DebtInstrumentCarryingAmount / us-gaap_DebtInstrumentAxis = cms_SeniorNotesEightMember / dei_LegalEntityAxis = us-gaap_ParentCompanyMember / us-gaap_LongtermDebtTypeAxis = us-gaap_UnsecuredDebtMember |  | 300,000,000 us-gaap_DebtInstrumentCarryingAmount / us-gaap_DebtInstrumentAxis = cms_SeniorNotesEightMember / dei_LegalEntityAxis = us-gaap_ParentCompanyMember / us-gaap_LongtermDebtTypeAxis = us-gaap_UnsecuredDebtMember |
Senior Notes [Member] | Senior Notes 6.250% Due 2020 [Member] | CMS Energy [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Interest rate | 6.25%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_DebtInstrumentAxis = cms_SeniorNotesNineMember / dei_LegalEntityAxis = us-gaap_ParentCompanyMember / us-gaap_LongtermDebtTypeAxis = us-gaap_UnsecuredDebtMember |  |  |
Maturity Date | 2020 |  |  |
Principal amounts outstanding | 300,000,000 us-gaap_DebtInstrumentCarryingAmount / us-gaap_DebtInstrumentAxis = cms_SeniorNotesNineMember / dei_LegalEntityAxis = us-gaap_ParentCompanyMember / us-gaap_LongtermDebtTypeAxis = us-gaap_UnsecuredDebtMember |  | 300,000,000 us-gaap_DebtInstrumentCarryingAmount / us-gaap_DebtInstrumentAxis = cms_SeniorNotesNineMember / dei_LegalEntityAxis = us-gaap_ParentCompanyMember / us-gaap_LongtermDebtTypeAxis = us-gaap_UnsecuredDebtMember |
Senior Notes [Member] | Senior Notes 5.050% Due 2022 [Member] | CMS Energy [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Interest rate | 5.05%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_DebtInstrumentAxis = cms_SeniorNotesTenMember / dei_LegalEntityAxis = us-gaap_ParentCompanyMember / us-gaap_LongtermDebtTypeAxis = us-gaap_UnsecuredDebtMember |  |  |
Maturity Date | 2022 |  |  |
Principal amounts outstanding | 300,000,000 us-gaap_DebtInstrumentCarryingAmount / us-gaap_DebtInstrumentAxis = cms_SeniorNotesTenMember / dei_LegalEntityAxis = us-gaap_ParentCompanyMember / us-gaap_LongtermDebtTypeAxis = us-gaap_UnsecuredDebtMember |  | 300,000,000 us-gaap_DebtInstrumentCarryingAmount / us-gaap_DebtInstrumentAxis = cms_SeniorNotesTenMember / dei_LegalEntityAxis = us-gaap_ParentCompanyMember / us-gaap_LongtermDebtTypeAxis = us-gaap_UnsecuredDebtMember |
Senior Notes [Member] | Senior Notes 3.875% Due March 2024 [Member] | CMS Energy [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Interest rate | 3.875%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_DebtInstrumentAxis = cms_SeniorNotesOneMember / dei_LegalEntityAxis = us-gaap_ParentCompanyMember / us-gaap_LongtermDebtTypeAxis = us-gaap_UnsecuredDebtMember |  |  |
Maturity Date | 2024 |  |  |
Principal amounts outstanding | 250,000,000 us-gaap_DebtInstrumentCarryingAmount / us-gaap_DebtInstrumentAxis = cms_SeniorNotesOneMember / dei_LegalEntityAxis = us-gaap_ParentCompanyMember / us-gaap_LongtermDebtTypeAxis = us-gaap_UnsecuredDebtMember |  |  |
Senior Notes [Member] | Senior Notes 5.500% Due June 2029 [Member] | CMS Energy [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Interest rate | 5.50%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_DebtInstrumentAxis = cms_SeniorNotesFourMember / dei_LegalEntityAxis = us-gaap_ParentCompanyMember / us-gaap_LongtermDebtTypeAxis = us-gaap_UnsecuredDebtMember | [7] |  |
Maturity Date | 2029 |  |  |
Principal amounts outstanding |  |  | 172,000,000 us-gaap_DebtInstrumentCarryingAmount / us-gaap_DebtInstrumentAxis = cms_SeniorNotesFourMember / dei_LegalEntityAxis = us-gaap_ParentCompanyMember / us-gaap_LongtermDebtTypeAxis = us-gaap_UnsecuredDebtMember |
Senior Notes [Member] | Senior Notes 4.700% Due 2043 [Member] | CMS Energy [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Interest rate | 4.70%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_DebtInstrumentAxis = cms_SeniorNotesElevenMember / dei_LegalEntityAxis = us-gaap_ParentCompanyMember / us-gaap_LongtermDebtTypeAxis = us-gaap_UnsecuredDebtMember |  |  |
Maturity Date | 2043 |  |  |
Principal amounts outstanding | 250,000,000 us-gaap_DebtInstrumentCarryingAmount / us-gaap_DebtInstrumentAxis = cms_SeniorNotesElevenMember / dei_LegalEntityAxis = us-gaap_ParentCompanyMember / us-gaap_LongtermDebtTypeAxis = us-gaap_UnsecuredDebtMember |  | 250,000,000 us-gaap_DebtInstrumentCarryingAmount / us-gaap_DebtInstrumentAxis = cms_SeniorNotesElevenMember / dei_LegalEntityAxis = us-gaap_ParentCompanyMember / us-gaap_LongtermDebtTypeAxis = us-gaap_UnsecuredDebtMember |
Senior Notes [Member] | Senior Notes 4.875% Due March 2044 [Member] | CMS Energy [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Interest rate | 4.875%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_DebtInstrumentAxis = cms_SeniorNotesTwoMember / dei_LegalEntityAxis = us-gaap_ParentCompanyMember / us-gaap_LongtermDebtTypeAxis = us-gaap_UnsecuredDebtMember |  |  |
Maturity Date | 2044 |  |  |
Principal amounts outstanding | 300,000,000 us-gaap_DebtInstrumentCarryingAmount / us-gaap_DebtInstrumentAxis = cms_SeniorNotesTwoMember / dei_LegalEntityAxis = us-gaap_ParentCompanyMember / us-gaap_LongtermDebtTypeAxis = us-gaap_UnsecuredDebtMember |  |  |
Other CMS Subsidiaries [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Principal amounts outstanding | 884,000,000 us-gaap_DebtInstrumentCarryingAmount / us-gaap_LongtermDebtTypeAxis = cms_OtherCmsSubsidiariesMember |  | 652,000,000 us-gaap_DebtInstrumentCarryingAmount / us-gaap_LongtermDebtTypeAxis = cms_OtherCmsSubsidiariesMember |
Other CMS Subsidiaries [Member] | EnerBank Certificates Of Deposit [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Interest rate | 1.218%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_DebtInstrumentAxis = us-gaap_CertificatesOfDepositMember / us-gaap_LongtermDebtTypeAxis = cms_OtherCmsSubsidiariesMember | [8] |  |
Maturity Date | 2015-2024 |  |  |
Interest-bearing Domestic Deposit, Brokered | 884,000,000 us-gaap_InterestBearingDomesticDepositBrokered / us-gaap_DebtInstrumentAxis = us-gaap_CertificatesOfDepositMember / us-gaap_LongtermDebtTypeAxis = cms_OtherCmsSubsidiariesMember |  | 652,000,000 us-gaap_InterestBearingDomesticDepositBrokered / us-gaap_DebtInstrumentAxis = us-gaap_CertificatesOfDepositMember / us-gaap_LongtermDebtTypeAxis = cms_OtherCmsSubsidiariesMember |
Weighted-average interest rate | 1.22%us-gaap_WeightedAverageRateDomesticDepositBrokered / us-gaap_DebtInstrumentAxis = us-gaap_CertificatesOfDepositMember / us-gaap_LongtermDebtTypeAxis = cms_OtherCmsSubsidiariesMember |  | 1.09%us-gaap_WeightedAverageRateDomesticDepositBrokered / us-gaap_DebtInstrumentAxis = us-gaap_CertificatesOfDepositMember / us-gaap_LongtermDebtTypeAxis = cms_OtherCmsSubsidiariesMember |
Certificate of deposit face value | 1,000 us-gaap_InvestmentOwnedUnderlyingFaceAmountAtMarketValue / us-gaap_DebtInstrumentAxis = us-gaap_CertificatesOfDepositMember / us-gaap_LongtermDebtTypeAxis = cms_OtherCmsSubsidiariesMember |  |  |
First Mortgage Bonds [Member] | Consumers Energy Company [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Principal amounts outstanding | 4,573,000,000 us-gaap_DebtInstrumentCarryingAmount / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_LongtermDebtTypeAxis = cms_FirstMortgageBondsMember | [3] | 4,250,000,000 us-gaap_DebtInstrumentCarryingAmount / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_LongtermDebtTypeAxis = cms_FirstMortgageBondsMember | [3]
Weighted-average Interest Rate (%) | 4.75%us-gaap_LongtermDebtWeightedAverageInterestRate / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_LongtermDebtTypeAxis = cms_FirstMortgageBondsMember |  | 4.90%us-gaap_LongtermDebtWeightedAverageInterestRate / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_LongtermDebtTypeAxis = cms_FirstMortgageBondsMember |
First Mortgage Bonds [Member] | FMB's 2.600% Due 2015 [Member] | Consumers Energy Company [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Interest rate | 2.60%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_DebtInstrumentAxis = cms_FirstMortgageBondsFourMember / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_LongtermDebtTypeAxis = cms_FirstMortgageBondsMember | [3],[9] |  |
Maturity Date | 2015 | [3] |  |
Principal amounts outstanding | 50,000,000 us-gaap_DebtInstrumentCarryingAmount / us-gaap_DebtInstrumentAxis = cms_FirstMortgageBondsFourMember / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_LongtermDebtTypeAxis = cms_FirstMortgageBondsMember | [3] | 50,000,000 us-gaap_DebtInstrumentCarryingAmount / us-gaap_DebtInstrumentAxis = cms_FirstMortgageBondsFourMember / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_LongtermDebtTypeAxis = cms_FirstMortgageBondsMember | [3]
First Mortgage Bonds [Member] | FMB's 5.500% Due August 2016 [Member] | Consumers Energy Company [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Interest rate | 5.50%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_DebtInstrumentAxis = cms_FirstMortgageBondsThreeMember / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_LongtermDebtTypeAxis = cms_FirstMortgageBondsMember | [3],[9] |  |
Maturity Date | 2016 | [3] |  |
Principal amounts outstanding | 173,000,000 us-gaap_DebtInstrumentCarryingAmount / us-gaap_DebtInstrumentAxis = cms_FirstMortgageBondsThreeMember / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_LongtermDebtTypeAxis = cms_FirstMortgageBondsMember | [3] | 350,000,000 us-gaap_DebtInstrumentCarryingAmount / us-gaap_DebtInstrumentAxis = cms_FirstMortgageBondsThreeMember / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_LongtermDebtTypeAxis = cms_FirstMortgageBondsMember | [3]
First Mortgage Bonds [Member] | FMB's 5.150% Due 2017 [Member] | Consumers Energy Company [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Interest rate | 5.15%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_DebtInstrumentAxis = cms_FirstMortgageBondsFiveMember / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_LongtermDebtTypeAxis = cms_FirstMortgageBondsMember | [3] |  |
Maturity Date | 2017 | [3] |  |
Principal amounts outstanding | 250,000,000 us-gaap_DebtInstrumentCarryingAmount / us-gaap_DebtInstrumentAxis = cms_FirstMortgageBondsFiveMember / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_LongtermDebtTypeAxis = cms_FirstMortgageBondsMember | [3] | 250,000,000 us-gaap_DebtInstrumentCarryingAmount / us-gaap_DebtInstrumentAxis = cms_FirstMortgageBondsFiveMember / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_LongtermDebtTypeAxis = cms_FirstMortgageBondsMember | [3]
First Mortgage Bonds [Member] | FMB's 3.210% Due 2017 [Member] | Consumers Energy Company [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Interest rate | 3.21%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_DebtInstrumentAxis = cms_FirstMortgageBondsSixMember / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_LongtermDebtTypeAxis = cms_FirstMortgageBondsMember | [3] |  |
Maturity Date | 2017 | [3] |  |
Principal amounts outstanding | 100,000,000 us-gaap_DebtInstrumentCarryingAmount / us-gaap_DebtInstrumentAxis = cms_FirstMortgageBondsSixMember / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_LongtermDebtTypeAxis = cms_FirstMortgageBondsMember | [3] | 100,000,000 us-gaap_DebtInstrumentCarryingAmount / us-gaap_DebtInstrumentAxis = cms_FirstMortgageBondsSixMember / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_LongtermDebtTypeAxis = cms_FirstMortgageBondsMember | [3]
First Mortgage Bonds [Member] | FMB's 5.650% Due 2018 [Member] | Consumers Energy Company [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Interest rate | 5.65%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_DebtInstrumentAxis = cms_FirstMortgageBondsSevenMember / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_LongtermDebtTypeAxis = cms_FirstMortgageBondsMember | [3] |  |
Maturity Date | 2018 | [3] |  |
Principal amounts outstanding | 250,000,000 us-gaap_DebtInstrumentCarryingAmount / us-gaap_DebtInstrumentAxis = cms_FirstMortgageBondsSevenMember / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_LongtermDebtTypeAxis = cms_FirstMortgageBondsMember | [3] | 250,000,000 us-gaap_DebtInstrumentCarryingAmount / us-gaap_DebtInstrumentAxis = cms_FirstMortgageBondsSevenMember / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_LongtermDebtTypeAxis = cms_FirstMortgageBondsMember | [3]
First Mortgage Bonds [Member] | FMB's 6.125% Due 2019 [Member] | Consumers Energy Company [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Interest rate | 6.125%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_DebtInstrumentAxis = cms_FirstMortgageBondsEightMember / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_LongtermDebtTypeAxis = cms_FirstMortgageBondsMember | [3] |  |
Maturity Date | 2019 | [3] |  |
Principal amounts outstanding | 350,000,000 us-gaap_DebtInstrumentCarryingAmount / us-gaap_DebtInstrumentAxis = cms_FirstMortgageBondsEightMember / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_LongtermDebtTypeAxis = cms_FirstMortgageBondsMember | [3] | 350,000,000 us-gaap_DebtInstrumentCarryingAmount / us-gaap_DebtInstrumentAxis = cms_FirstMortgageBondsEightMember / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_LongtermDebtTypeAxis = cms_FirstMortgageBondsMember | [3]
First Mortgage Bonds [Member] | FMB's 6.700% Due 2019 [Member] | Consumers Energy Company [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Interest rate | 6.70%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_DebtInstrumentAxis = cms_FirstMortgageBondsNineMember / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_LongtermDebtTypeAxis = cms_FirstMortgageBondsMember | [3] |  |
Maturity Date | 2019 | [3] |  |
Principal amounts outstanding | 500,000,000 us-gaap_DebtInstrumentCarryingAmount / us-gaap_DebtInstrumentAxis = cms_FirstMortgageBondsNineMember / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_LongtermDebtTypeAxis = cms_FirstMortgageBondsMember | [3] | 500,000,000 us-gaap_DebtInstrumentCarryingAmount / us-gaap_DebtInstrumentAxis = cms_FirstMortgageBondsNineMember / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_LongtermDebtTypeAxis = cms_FirstMortgageBondsMember | [3]
First Mortgage Bonds [Member] | FMB's 5.650% Due 2020 [Member] | Consumers Energy Company [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Interest rate | 5.65%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_DebtInstrumentAxis = cms_FirstMortgageBondsTenMember / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_LongtermDebtTypeAxis = cms_FirstMortgageBondsMember | [3] |  |
Maturity Date | 2020 | [3] |  |
Principal amounts outstanding | 300,000,000 us-gaap_DebtInstrumentCarryingAmount / us-gaap_DebtInstrumentAxis = cms_FirstMortgageBondsTenMember / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_LongtermDebtTypeAxis = cms_FirstMortgageBondsMember | [3] | 300,000,000 us-gaap_DebtInstrumentCarryingAmount / us-gaap_DebtInstrumentAxis = cms_FirstMortgageBondsTenMember / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_LongtermDebtTypeAxis = cms_FirstMortgageBondsMember | [3]
First Mortgage Bonds [Member] | FMB's 3.770% Due 2020 [Member] | Consumers Energy Company [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Interest rate | 3.77%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_DebtInstrumentAxis = cms_FirstMortgageBondsElevenMember / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_LongtermDebtTypeAxis = cms_FirstMortgageBondsMember | [3] |  |
Maturity Date | 2020 | [3] |  |
Principal amounts outstanding | 100,000,000 us-gaap_DebtInstrumentCarryingAmount / us-gaap_DebtInstrumentAxis = cms_FirstMortgageBondsElevenMember / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_LongtermDebtTypeAxis = cms_FirstMortgageBondsMember | [3] | 100,000,000 us-gaap_DebtInstrumentCarryingAmount / us-gaap_DebtInstrumentAxis = cms_FirstMortgageBondsElevenMember / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_LongtermDebtTypeAxis = cms_FirstMortgageBondsMember | [3]
First Mortgage Bonds [Member] | FMB's 5.300% Due 2022 [Member] | Consumers Energy Company [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Interest rate | 5.30%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_DebtInstrumentAxis = cms_FirstMortgageBondsTwelveMember / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_LongtermDebtTypeAxis = cms_FirstMortgageBondsMember | [3] |  |
Maturity Date | 2022 | [3] |  |
Principal amounts outstanding | 250,000,000 us-gaap_DebtInstrumentCarryingAmount / us-gaap_DebtInstrumentAxis = cms_FirstMortgageBondsTwelveMember / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_LongtermDebtTypeAxis = cms_FirstMortgageBondsMember | [3] | 250,000,000 us-gaap_DebtInstrumentCarryingAmount / us-gaap_DebtInstrumentAxis = cms_FirstMortgageBondsTwelveMember / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_LongtermDebtTypeAxis = cms_FirstMortgageBondsMember | [3]
First Mortgage Bonds [Member] | FMB's 2.850% Due 2022 [Member] | Consumers Energy Company [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Interest rate | 2.85%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_DebtInstrumentAxis = cms_FirstMortgageBondsThirteenMember / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_LongtermDebtTypeAxis = cms_FirstMortgageBondsMember | [3] |  |
Maturity Date | 2022 | [3] |  |
Principal amounts outstanding | 375,000,000 us-gaap_DebtInstrumentCarryingAmount / us-gaap_DebtInstrumentAxis = cms_FirstMortgageBondsThirteenMember / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_LongtermDebtTypeAxis = cms_FirstMortgageBondsMember | [3] | 375,000,000 us-gaap_DebtInstrumentCarryingAmount / us-gaap_DebtInstrumentAxis = cms_FirstMortgageBondsThirteenMember / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_LongtermDebtTypeAxis = cms_FirstMortgageBondsMember | [3]
First Mortgage Bonds [Member] | FMB's 3.375% Due 2023 [Member] | Consumers Energy Company [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Interest rate | 3.375%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_DebtInstrumentAxis = cms_FirstMortgageBondsFourteenMember / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_LongtermDebtTypeAxis = cms_FirstMortgageBondsMember | [3] |  |
Maturity Date | 2023 | [3] |  |
Principal amounts outstanding | 325,000,000 us-gaap_DebtInstrumentCarryingAmount / us-gaap_DebtInstrumentAxis = cms_FirstMortgageBondsFourteenMember / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_LongtermDebtTypeAxis = cms_FirstMortgageBondsMember | [3] | 325,000,000 us-gaap_DebtInstrumentCarryingAmount / us-gaap_DebtInstrumentAxis = cms_FirstMortgageBondsFourteenMember / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_LongtermDebtTypeAxis = cms_FirstMortgageBondsMember | [3]
First Mortgage Bonds [Member] | FMB's 3.190% Due 2024 [Member] | Consumers Energy Company [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Interest rate | 3.19%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_DebtInstrumentAxis = cms_FirstMortgageBondsFifteenMember / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_LongtermDebtTypeAxis = cms_FirstMortgageBondsMember | [3] |  |
Maturity Date | 2024 | [3] |  |
Principal amounts outstanding | 52,000,000 us-gaap_DebtInstrumentCarryingAmount / us-gaap_DebtInstrumentAxis = cms_FirstMortgageBondsFifteenMember / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_LongtermDebtTypeAxis = cms_FirstMortgageBondsMember | [3] | 52,000,000 us-gaap_DebtInstrumentCarryingAmount / us-gaap_DebtInstrumentAxis = cms_FirstMortgageBondsFifteenMember / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_LongtermDebtTypeAxis = cms_FirstMortgageBondsMember | [3]
First Mortgage Bonds [Member] | FMB's 3.390% Due 2027 [Member] | Consumers Energy Company [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Interest rate | 3.39%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_DebtInstrumentAxis = cms_FirstMortgageBondsSeventeenMember / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_LongtermDebtTypeAxis = cms_FirstMortgageBondsMember | [3] |  |
Maturity Date | 2027 | [3] |  |
Principal amounts outstanding | 35,000,000 us-gaap_DebtInstrumentCarryingAmount / us-gaap_DebtInstrumentAxis = cms_FirstMortgageBondsSeventeenMember / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_LongtermDebtTypeAxis = cms_FirstMortgageBondsMember | [3] | 35,000,000 us-gaap_DebtInstrumentCarryingAmount / us-gaap_DebtInstrumentAxis = cms_FirstMortgageBondsSeventeenMember / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_LongtermDebtTypeAxis = cms_FirstMortgageBondsMember | [3]
First Mortgage Bonds [Member] | FMB's 5.800% Due 2035 [Member] | Consumers Energy Company [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Interest rate | 5.80%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_DebtInstrumentAxis = cms_FirstMortgageBondsEighteenMember / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_LongtermDebtTypeAxis = cms_FirstMortgageBondsMember | [3] |  |
Maturity Date | 2035 | [3] |  |
Principal amounts outstanding | 175,000,000 us-gaap_DebtInstrumentCarryingAmount / us-gaap_DebtInstrumentAxis = cms_FirstMortgageBondsEighteenMember / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_LongtermDebtTypeAxis = cms_FirstMortgageBondsMember | [3] | 175,000,000 us-gaap_DebtInstrumentCarryingAmount / us-gaap_DebtInstrumentAxis = cms_FirstMortgageBondsEighteenMember / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_LongtermDebtTypeAxis = cms_FirstMortgageBondsMember | [3]
First Mortgage Bonds [Member] | FMB's 6.170% Due 2040 [Member] | Consumers Energy Company [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Interest rate | 6.17%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_DebtInstrumentAxis = cms_FirstMortgageBondsNineteenMember / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_LongtermDebtTypeAxis = cms_FirstMortgageBondsMember | [3] |  |
Maturity Date | 2040 | [3] |  |
Principal amounts outstanding | 50,000,000 us-gaap_DebtInstrumentCarryingAmount / us-gaap_DebtInstrumentAxis = cms_FirstMortgageBondsNineteenMember / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_LongtermDebtTypeAxis = cms_FirstMortgageBondsMember | [3] | 50,000,000 us-gaap_DebtInstrumentCarryingAmount / us-gaap_DebtInstrumentAxis = cms_FirstMortgageBondsNineteenMember / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_LongtermDebtTypeAxis = cms_FirstMortgageBondsMember | [3]
First Mortgage Bonds [Member] | FMB's 4.970% Due 2040 [Member] | Consumers Energy Company [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Interest rate | 4.97%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_DebtInstrumentAxis = cms_FirstMortgageBondsTwentyMember / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_LongtermDebtTypeAxis = cms_FirstMortgageBondsMember | [3] |  |
Maturity Date | 2040 | [3] |  |
Principal amounts outstanding | 50,000,000 us-gaap_DebtInstrumentCarryingAmount / us-gaap_DebtInstrumentAxis = cms_FirstMortgageBondsTwentyMember / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_LongtermDebtTypeAxis = cms_FirstMortgageBondsMember | [3] | 50,000,000 us-gaap_DebtInstrumentCarryingAmount / us-gaap_DebtInstrumentAxis = cms_FirstMortgageBondsTwentyMember / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_LongtermDebtTypeAxis = cms_FirstMortgageBondsMember | [3]
First Mortgage Bonds [Member] | FMB's 4.310% Due 2042 [Member] | Consumers Energy Company [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Interest rate | 4.31%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_DebtInstrumentAxis = cms_FirstMortgageBondsTwentyOneMember / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_LongtermDebtTypeAxis = cms_FirstMortgageBondsMember | [3] |  |
Maturity Date | 2042 | [3] |  |
Principal amounts outstanding | 263,000,000 us-gaap_DebtInstrumentCarryingAmount / us-gaap_DebtInstrumentAxis = cms_FirstMortgageBondsTwentyOneMember / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_LongtermDebtTypeAxis = cms_FirstMortgageBondsMember | [3] | 263,000,000 us-gaap_DebtInstrumentCarryingAmount / us-gaap_DebtInstrumentAxis = cms_FirstMortgageBondsTwentyOneMember / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_LongtermDebtTypeAxis = cms_FirstMortgageBondsMember | [3]
First Mortgage Bonds [Member] | FMB's 3.950% Due 2043 [Member] | Consumers Energy Company [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Interest rate | 3.95%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_DebtInstrumentAxis = cms_FirstMortgageBondsTwentyTwoMember / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_LongtermDebtTypeAxis = cms_FirstMortgageBondsMember | [3] |  |
Maturity Date | 2043 | [3] |  |
Principal amounts outstanding | 425,000,000 us-gaap_DebtInstrumentCarryingAmount / us-gaap_DebtInstrumentAxis = cms_FirstMortgageBondsTwentyTwoMember / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_LongtermDebtTypeAxis = cms_FirstMortgageBondsMember | [3] | 425,000,000 us-gaap_DebtInstrumentCarryingAmount / us-gaap_DebtInstrumentAxis = cms_FirstMortgageBondsTwentyTwoMember / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_LongtermDebtTypeAxis = cms_FirstMortgageBondsMember | [3]
First Mortgage Bonds [Member] | FMB's 4.350% Due August 2064 [Member] | Consumers Energy Company [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Interest rate | 4.35%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_DebtInstrumentAxis = cms_FirstMortgageBondsTwoMember / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_LongtermDebtTypeAxis = cms_FirstMortgageBondsMember | [3] |  |
Maturity Date | 2064 | [3] |  |
Principal amounts outstanding | $ 250,000,000 us-gaap_DebtInstrumentCarryingAmount / us-gaap_DebtInstrumentAxis = cms_FirstMortgageBondsTwoMember / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_LongtermDebtTypeAxis = cms_FirstMortgageBondsMember | [3] |  |
[1] | CMS Energy retired this debt at a premium and recorded a loss on extinguishment of $13 million in other expense on its consolidated statements of income.
[2] | CMS Energy retired this debt at a premium and recorded a loss on extinguishment of $7 million in other expense on its consolidated statements of income.
[3] | The weighted-average interest rate for Consumers’ FMBs was 4.75 percent at December 31, 2014 and 4.90 percent at December 31, 2013.
[4] | The interest rate for Consumers’ Securitization bonds issued through its subsidiary Consumers Funding was 5.76 percent at December 31, 2014 and 2013.The weighted-average interest rate for Consumers’ Securitization bonds issued through its subsidiary Consumers 2014 Securitization Funding was 2.60 percent at December 31, 2014.Principal and interest payments are made semiannually beginning in 2015.
[5] | In April 2014, CMS Energy retired its 6.875 percent senior notes.
[6] | In December 2014, CMS Energy retired its 4.25 percent senior notes.
[7] | In June 2014, CMS Energy retired its remaining 5.50 percent contingently convertible notes. See the “Contingently Convertible Securities” section in this Note for further discussion of the conversions.
[8] | The weighted-average interest rate for EnerBank’s certificates of deposit was 1.22 percent at December 31, 2014 and 1.09 percent at December 31, 2013. EnerBank’s primary deposit product consists of brokered certificates of deposit with varying maturities and having a face value of $1,000.
[9] | In August 2014, Consumers retired $177 million of its 5.50 percent FMBs.

X
- Definition Percentage points added to the reference rate to compute the variable rate on the debt instrument. + References No definition available. + Details
Name: | us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of long-term debt before deduction of unamortized discount or premium. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt, with initial maturities beyond one year or the normal operating cycle, if longer. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 20 -Article 5 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.22) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 22 -Article 5 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 16 -Article 9 + Details
Name: | us-gaap_DebtInstrumentCarryingAmount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Effective interest rate for the funds borrowed under the debt agreement considering interest compounding and original issue discount or premium. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 30 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6451184&loc=d3e28551-108399 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 22 -Article 5 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.22(a)(1)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
Name: | us-gaap_DebtInstrumentInterestRateEffectivePercentage
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Contractual interest rate for funds borrowed, under the debt agreement. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 22 -Article 5 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.22(a)(1)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
Name: | us-gaap_DebtInstrumentInterestRateStatedPercentage
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

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

X
- Definition Description of the maturity date of the debt instrument including whether the debt matures serially and, if so, a brief description of the serial maturities. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 22 -Article 5 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.22(a)(2)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
Name: | us-gaap_DebtInstrumentMaturityDateDescription
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition The amount of debt discount (net of debt premium) that was originally recognized at the issuance of the instrument that has yet to be amortized. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 30 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6451184&loc=d3e28551-108399 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 30 -Section 45 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=6451184&loc=d3e28555-108399 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 30 -Section 45 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=6451184&loc=d3e28567-108399 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 30 -Section 45 -Paragraph 1A -URI http://asc.fasb.org/extlink&oid=6451184&loc=d3e28541-108399 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 30 -Section 55 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=34725769&loc=d3e28878-108400 + Details
Name: | us-gaap_DebtInstrumentUnamortizedDiscountPremiumNet
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of interest-bearing domestic third-party deposits placed by or through the assistance of a deposit broker, also known as brokered deposit liabilities. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03.12) -URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 12 -Article 9 + Details
Name: | us-gaap_InterestBearingDomesticDepositBrokered
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Nominal or face amount on the investment owned. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Underlying -URI http://asc.fasb.org/extlink&oid=6527499 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 10 -Paragraph 1 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=6431724&loc=d3e32938-113948 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 20 -Section 10 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6438156&loc=d3e57880-113973 + Details
Name: | us-gaap_InvestmentOwnedUnderlyingFaceAmountAtMarketValue
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of long-term debt, after unamortized discount or premium, scheduled to be repaid within one year or the normal operating cycle, if longer. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.19,20) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 20 -Article 5 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 19 -Article 5 + Details
Name: | us-gaap_LongTermDebtCurrent
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Carrying amount of long-term debt, net of unamortized discount or premium, excluding amounts to be repaid within one year or the normal operating cycle, if longer (current maturities). Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.22) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 22 -Article 5 + Details
Name: | us-gaap_LongTermDebtNoncurrent
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Weighted average interest rate of long-term debt outstanding. + References No definition available. + Details
Name: | us-gaap_LongtermDebtWeightedAverageInterestRate
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition The cash outflow during the period from the repayment of aggregate short-term and long-term debt. Excludes payment of capital lease obligations. + References No definition available. + Details
Name: | us-gaap_RepaymentsOfDebt
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition The weighted average interest rate for domestic brokered deposit liabilities. + References No definition available. + Details
Name: | us-gaap_WeightedAverageRateDomesticDepositBrokered
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Details
Name: | dei_LegalEntityAxis=cms_ConsumersEnergyCompanyMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | dei_LegalEntityAxis=us-gaap_ParentCompanyMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=cms_FirstMortgageBondsOneMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=cms_FirstMortgageBondsThreeMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=cms_FirstMortgageBondsTwoMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=cms_PollutionControlRevenueBondsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=cms_SecuritizationBondsFiveMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=cms_SecuritizationBondsFourMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=cms_SecuritizationBondsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=cms_SeniorNotesFiveMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=cms_SeniorNotesFourMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=cms_SeniorNotesOneMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=cms_SeniorNotesThreeMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=cms_SeniorNotesTwelveMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=cms_SeniorNotesTwoMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=cms_ShortTermLoanFacilityOneMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_LongtermDebtTypeAxis=cms_FirstMortgageBondsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_LongtermDebtTypeAxis=cms_OtherCmsSubsidiariesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_LongtermDebtTypeAxis=us-gaap_UnsecuredDebtMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |