Financings And Capitalization (Narrative) (Details) - USD ($)	1 Months Ended	12 Months Ended
	Aug. 31, 2018	Dec. 31, 2018	Dec. 28, 2018	Dec. 31, 2017
Financing And Capitalization [Line Items]
Limitation on payment of stock dividends		$ 4,800,000,000
Dividends paid		$ 531,000,000
Common stock authorized (in shares)		350,000,000		350,000,000
Par value of common stock (in dollars per share)		$ 0.01
Preferred stock authorized (in shares)		10,000,000
Par value of preferred stock (in dollars per share)		$ 0.01
Stock offering program maximum value	$ 250,000,000	$ 100,000,000
Number of shares required to settle forward contracts (in shares)		463
Consumers Energy Company
Financing And Capitalization [Line Items]
Unrestricted retained earnings		$ 1,300,000,000
Common stock authorized (in shares)		125,000,000		125,000,000
Interest rate coverage ratio multiplier minimum to issue FMBs		200.00%
Consumers Energy Company | Commercial Paper
Financing And Capitalization [Line Items]
Short-term debt authorized borrowings		$ 500,000,000
Short-term borrowings outstanding		$ 97,000,000
Weighted average annual interest rate		2.913%
Term loans and revolving credit agreements
Financing And Capitalization [Line Items]
Amount of Facility			$ 300,000,000