Retirement Benefits (Schedule Of Net Periodic Benefit Cost Not yet Recognized) (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Consumers Energy Company
Regulatory assets (liabilities)
Total regulatory assets	$ 2,305	$ 2,695
Total regulatory liabilities	(3,948)	(3,895)
DB Pension Plans and DB SERP
Regulatory assets (liabilities)
Net loss	812	1,194
Prior service cost (credit)	25	29
Total regulatory assets	837	1,223
AOCI
Net loss (gain)	94	120
Prior service cost (credit)	0	1
Total amounts recognized in regulatory assets (liabilities) and AOCI	931	1,344
DB Pension Plans and DB SERP | Consumers Energy Company
Regulatory assets (liabilities)
Net loss	812	1,194
Prior service cost (credit)	25	29
Total regulatory assets	837	1,223
AOCI
Net loss (gain)	41	47
Total amounts recognized in regulatory assets (liabilities) and AOCI	878	1,270
OPEB Plan
Regulatory assets (liabilities)
Net loss	136	254
Prior service cost (credit)	(190)	(246)
Total regulatory assets		8
Total regulatory liabilities	(54)
AOCI
Net loss (gain)	(17)	(10)
Prior service cost (credit)	(5)	(6)
Total amounts recognized in regulatory assets (liabilities) and AOCI	(76)	(8)
OPEB Plan | Consumers Energy Company
Regulatory assets (liabilities)
Net loss	136	254
Prior service cost (credit)	(190)	(246)
Total regulatory assets		8
Total regulatory liabilities	(54)
AOCI
Net loss (gain)	0	0
Total amounts recognized in regulatory assets (liabilities) and AOCI	$ (54)	$ 8