Retirement Benefits (Schedule Of Plan Contributions) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Postretirement benefits contributions	$ 10	$ 252	$ 12
Consumers Energy Company
Defined Benefit Plan Disclosure [Line Items]
Postretirement benefits contributions	7	242	$ 8
DB Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Postretirement benefits contributions	0	240
DB Pension Plans | Consumers Energy Company
Defined Benefit Plan Disclosure [Line Items]
Postretirement benefits contributions	$ 0	$ 234