Financings And Capitalization (Narrative) (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jul. 26, 2018
Financing And Capitalization [Line Items]
Principal balance	$ 750,000,000		$ 750,000,000
Unrestricted retained earnings	4,700,000,000		4,700,000,000
Common stock dividends from Consumers			245,000,000
Stock offering program maximum value		$ 100,000,000
Consumers Energy Company
Financing And Capitalization [Line Items]
Principal balance	550,000,000		550,000,000
Unrestricted retained earnings	1,300,000,000		1,300,000,000
Consumers Energy Company | Commercial Paper
Financing And Capitalization [Line Items]
Short-term debt, authorized borrowings	500,000,000
Short-term debt	$ 0		$ 0
Subsequent Event | October 2018 First Mortgage Bonds | Consumers Energy Company
Financing And Capitalization [Line Items]
Principal balance				$ 500,000,000