Financings and Capitalization (Narrative) (Details) - USD ($)		1 Months Ended		6 Months Ended		12 Months Ended	24 Months Ended
	Jun. 30, 2020	Apr. 30, 2020	Mar. 31, 2020	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2018	Dec. 31, 2019	Jul. 31, 2020
Financing And Capitalization [Line Items]
Amount available for dividend payments	$ 5,200,000,000			$ 5,200,000,000
Common stock dividends from Consumers				276,000,000
Stock offering program maximum value		$ 500,000,000				$ 250,000,000
Proceeds from settlement of forward contracts				$ 104,000,000	$ 6,000,000
Settlement required (in shares)	390,008			390,008
Consumers Energy Company
Financing And Capitalization [Line Items]
Unrestricted retained earnings	$ 1,600,000,000			$ 1,600,000,000
Consumers Energy Company | Commercial Paper
Financing And Capitalization [Line Items]
Short-term debt, authorized borrowings				500,000,000
Short-term debt	0			$ 0
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
Subsequent Event | Tax Exempt Revenue Bonds | Tax Exempt Revenue Bonds Due 2035 | Consumers Energy Company
Financing And Capitalization [Line Items]
Debt repurchased								$ 35,000,000