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Financings And Capitalization (Narrative) (Details) - USD ($) | 3 Months Ended | 6 Months Ended |
--- | --- | --- | ---
Jun. 30, 2018 | Jun. 30, 2017 | Jun. 30, 2018 | Jul. 26, 2018
Financing And Capitalization [Line Items] |  |  |  |
Principal balance | $ 750,000,000 |  | $ 750,000,000 |
Unrestricted retained earnings | 4,700,000,000 |  | 4,700,000,000 |
Common stock dividends from Consumers |  |  | 245,000,000 |
Stock offering program maximum value |  | $ 100,000,000 |  |
Consumers Energy Company |  |  |  |
Financing And Capitalization [Line Items] |  |  |  |
Principal balance | 550,000,000 |  | 550,000,000 |
Unrestricted retained earnings | 1,300,000,000 |  | 1,300,000,000 |
Consumers Energy Company | Commercial Paper |  |  |  |
Financing And Capitalization [Line Items] |  |  |  |
Short-term debt, authorized borrowings | 500,000,000 |  |  |
Short-term debt | $ 0 |  | $ 0 |
Subsequent Event | October 2018 First Mortgage Bonds | Consumers Energy Company |  |  |  |
Financing And Capitalization [Line Items] |  |  |  |
Principal balance |  |  |  | $ 500,000,000

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