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Financings And Capitalization (Narrative) (Details) - USD ($) | 1 Months Ended | 3 Months Ended
--- | --- | ---
Dec. 31, 2020 | Mar. 31, 2021
Financing And Capitalization [Line Items] |  |
Limitation on payment of stock dividends |  | $ 5,700,000,000
Dividends paid |  | 276,000,000
Stock offering program maximum value |  | $ 500,000,000
Number of shares required to settle forward contracts (in shares) |  | 16,758
Consumers Energy Company |  |
Financing And Capitalization [Line Items] |  |
Notes payable – related parties | $ 307,000,000 | $ 57,000,000
Unrestricted retained earnings |  | 1,700,000,000
Consumers Energy Company | Credit Agreement |  |
Financing And Capitalization [Line Items] |  |
Maximum borrowing capacity | $ 350,000,000 |
Notes payable – related parties |  | $ 57,000,000
Weighted average interest rate |  | 0.014%
Consumers Energy Company | Credit Agreement | London Interbank Offered Rate (LIBOR) |  |
Financing And Capitalization [Line Items] |  |
Basis spread on variable rate | 0.10% |
Consumers Energy Company | Commercial Paper |  |
Financing And Capitalization [Line Items] |  |
Short-term debt authorized borrowings |  | $ 500,000,000
Short-term borrowings outstanding |  | $ 0

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