Retirement Benefits (Schedule of Net Periodic Benefit Cost Not yet Recognized) (Details) - USD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023
Consumers Energy Company
Regulatory assets
Total regulatory assets	$ 3,798	$ 3,886
DB Pension Plans and DB SERP
Regulatory assets
Net loss	653	634
Prior service cost (credit)	12	16
Total regulatory assets	665	650
AOCI
Net loss (gain)	60	65
Prior service cost (credit)	0	1
Total amounts recognized in regulatory assets and AOCI	725	716
DB Pension Plans and DB SERP | Consumers Energy Company
Regulatory assets
Net loss	653	634
Prior service cost (credit)	12	16
Total regulatory assets	665	650
AOCI
Net loss (gain)	15	20
Total amounts recognized in regulatory assets and AOCI	680	670
OPEB Plan
Regulatory assets
Net loss	176	191
Prior service cost (credit)	(94)	(100)
Total regulatory assets	82	91
AOCI
Net loss (gain)	(3)	(3)
Prior service cost (credit)	(2)	(2)
Total amounts recognized in regulatory assets and AOCI	77	86
OPEB Plan | Consumers Energy Company
Regulatory assets
Net loss	176	191
Prior service cost (credit)	(94)	(100)
Total regulatory assets	82	91
AOCI
Net loss (gain)	0	0
Total amounts recognized in regulatory assets and AOCI	$ 82	$ 91