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Financings And Capitalization (Major Long-Term Debt Transactions) (Details) - CMS Energy [Member] | 3 Months Ended
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Mar. 31, 2018 USD ($)
Junior Subordinated Notes 5.625% Due March 2078 [Member] |  |
Debt Instrument [Line Items] |  |
Principal Balance | $ 200,000,000 | [1]
Interest rate | 5.625% | [1]
Debt issuance date | March 2018 | [1]
Maturity date | 2078-03 | [1]
Term Loan Facility Due 2018 [Member] |  |
Debt Instrument [Line Items] |  |
Debt retirement, principal | $ 180,000,000 |
Debt retirement date | March 2018 |
Maturity date | 2018-12 |
[1] | These unsecured obligations rank subordinate and junior in right of payment to all of CMS Energy's existing and future senior indebtedness.

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- Definition Date when the debt instrument was partially or fully repaid, which may be presented in a variety of ways (year, month and year, day, month and year, quarter, etc.). + References No definition available. + Details
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