Retirement Benefits (Schedule Of Retirement Benefit Plan Assets (Liabilities)) (Details) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021
Defined Benefit Plan Disclosure [Line Items]
Non-current assets	$ 1,208	$ 1,150
Non-current liabilities	108	142
Consumers Energy Company
Defined Benefit Plan Disclosure [Line Items]
Non-current assets	1,126	1,056
Non-current liabilities	79	104
DB Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Non-current assets	651	529
DB Pension Plans | Consumers Energy Company
Defined Benefit Plan Disclosure [Line Items]
Non-current assets	632	510
OPEB Plan
Defined Benefit Plan Disclosure [Line Items]
Non-current assets	557	621
OPEB Plan | Consumers Energy Company
Defined Benefit Plan Disclosure [Line Items]
Non-current assets	494	546
DB SERP
Defined Benefit Plan Disclosure [Line Items]
Current liabilities	10	10
Non-current liabilities	107	139
DB SERP | Consumers Energy Company
Defined Benefit Plan Disclosure [Line Items]
Current liabilities	7	7
Non-current liabilities	$ 78	$ 102