Financings And Capitalization (Narrative) (Details)		1 Months Ended		9 Months Ended
	Jul. 01, 2021 USD ($) $ / shares shares	Oct. 28, 2021 USD ($)	Dec. 31, 2020 USD ($)	Sep. 30, 2021 USD ($) shares	Sep. 30, 2020 USD ($)	Jul. 31, 2020 USD ($)
Financing And Capitalization [Line Items]
Limitation on payment of stock dividends				$ 5,900,000,000
Dividends paid				570,000,000
Stock offering program maximum value				$ 500,000,000
Number of shares required to settle forward contracts (in shares) | shares				10,266
Issuance of preferred stock, net of issuance costs				$ 224,000,000	$ 0
Term Loan Facility Due November 2021 | Subsequent Event
Financing And Capitalization [Line Items]
Debt retirement, principal		$ 200,000,000
Series C Preferred Stock Depositary Shares
Financing And Capitalization [Line Items]
Number of shares issued (in shares) | shares	9,200,000
Depositary share conversion ratio	0.001
Issue price (in dollars per share) | $ / shares	$ 25.00
Issuance of preferred stock, net of issuance costs	$ 224,000,000
Dividend rate	4.20%
Optional redemption price (in dollars per share) | $ / shares	$ 25.00
Series C Preferred Stock
Financing And Capitalization [Line Items]
Optional redemption price (in dollars per share) | $ / shares	$ 25,000
Consumers Energy Company
Financing And Capitalization [Line Items]
Notes payable – related parties			$ 307,000,000	0
Unrestricted retained earnings				1,800,000,000
Consumers Energy Company | Tax Exempt Revenue Bonds Due 2035 | Tax Exempt Revenue Bonds
Financing And Capitalization [Line Items]
Debt repurchased						$ 35,000,000
Consumers Energy Company | Tax Exempt Revenue Bonds Due 2026 | Tax Exempt Revenue Bonds | Subsequent Event
Financing And Capitalization [Line Items]
Debt reissued		$ 35,000,000
Interest rate		0.875%
Consumers Energy Company | Credit Agreement
Financing And Capitalization [Line Items]
Maximum borrowing capacity			$ 350,000,000
Notes payable – related parties				0
Consumers Energy Company | Credit Agreement | Subsequent Event
Financing And Capitalization [Line Items]
Maximum borrowing capacity		$ 500,000,000
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