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Financings And Capitalization (Major Long-Term Debt Transactions) (Details) | 6 Months Ended
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Jun. 30, 2017 USD ($)
Senior Notes 3.450% Due August 2027 [Member] | CMS Energy [Member] |
Debt Instrument [Line Items] |
Principal Balance | $ 350,000,000
Interest rate | 3.45%
Debt issuance date | February 2017
Maturity date | August 2027
FMB's 3.950% Due July 2047 [Member] | Consumers Energy Company [Member] |
Debt Instrument [Line Items] |
Principal Balance | $ 350,000,000
Interest rate | 3.95%
Debt issuance date | February 2017
Maturity date | July 2047
FMB's 5.150% Due February 2017 [Member] | Consumers Energy Company [Member] |
Debt Instrument [Line Items] |
Debt retirement, principal | $ 250,000,000
Interest rate | 5.15%
Debt retirement date | February 2017
Maturity date | February 2017

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