Financings and Capitalization (Narrative) (Details) - USD ($)		1 Months Ended		3 Months Ended		12 Months Ended	24 Months Ended
	Mar. 31, 2020	Apr. 27, 2020	Mar. 31, 2020	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2018	Dec. 31, 2019
Financing And Capitalization [Line Items]
Amount available for dividend payments	$ 5,200,000,000		$ 5,200,000,000	$ 5,200,000,000
Common stock dividends from Consumers				219,000,000
Stock offering program maximum value						$ 250,000,000
Proceeds from settlement of forward contracts				$ 101,000,000	$ 3,000,000
Settlement required (in shares)	379,776		379,776	379,776
Consumers Energy Company
Financing And Capitalization [Line Items]
Unrestricted retained earnings	$ 1,500,000,000		$ 1,500,000,000	$ 1,500,000,000
Consumers Energy Company | Commercial Paper
Financing And Capitalization [Line Items]
Short-term debt, authorized borrowings				500,000,000
Short-term debt	0		$ 0	$ 0
Forward Contracts
Financing And Capitalization [Line Items]
Forward sales contracts aggregate price	$ 150,000,000						$ 250,000,000
Settlement of Forward Contracts
Financing And Capitalization [Line Items]
Settlement of forward contract issued (in shares)			2,017,783
Forward contract settlement (in dollars per share)			$ 47.95
Proceeds from settlement of forward contracts			$ 97,000,000
First Mortgage Bonds due October 2020 | Subsequent Event | Consumers Energy Company
Financing And Capitalization [Line Items]
Interest Rate		3.77%
First Mortgage Bonds | First Mortgage Bonds due October 2020 | Subsequent Event | Consumers Energy Company
Financing And Capitalization [Line Items]
Redemption of debt		$ 100,000,000