Financings And Capitalization (Narrative) (Details) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended	3 Months Ended		12 Months Ended
	Apr. 25, 2018	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Financing And Capitalization [Line Items]
Unrestricted retained earnings		$ 4,600
Common stock dividends from Consumers		119
Stock Offering Program Maximum Value			$ 100
Number of Shares Issued				1,494,371
Average Price Per Share				$ 47.31
Net Proceeds				$ 70
Consumers Energy Company [Member]
Financing And Capitalization [Line Items]
Unrestricted retained earnings		1,200
Consumers Energy Company [Member] | Commercial Paper [Member]
Financing And Capitalization [Line Items]
Short-term debt, authorized borrowings		500
Short-term borrowings outstanding		$ 0
Consumers Energy Company [Member] | Tax-Exempt Pollution Control Revenue Bonds [Member] | Subsequent Event [Member]
Financing And Capitalization [Line Items]
Debt retirement, principal	$ 68