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