Retirement Benefits (Schedule of Net Benefit Costs) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
DB Pension Plans
Defined Benefit Plan, Roll Forwards [Abstract]
Service cost	$ 7	$ 8	$ 14	$ 15
Interest cost	26	26	52	53
Expected return on plan assets	(59)	(55)	(118)	(110)
Amortization of:
Net loss	3	3	6	6
Prior service cost (credit)	1	1	2	2
Settlement loss	2	3	5	5
Net periodic credit	(20)	(14)	(39)	(29)
DB Pension Plans | Volatility Mechanism
Amortization of:
Deferred credits			9
DB Pension Plans | Consumers Energy Company
Defined Benefit Plan, Roll Forwards [Abstract]
Service cost	6	7	13	14
Interest cost	25	26	49	51
Expected return on plan assets	(55)	(52)	(110)	(104)
Amortization of:
Net loss	2	2	5	5
Prior service cost (credit)	1	1	2	2
Settlement loss	2	3	5	5
Net periodic credit	(19)	(13)	(36)	(27)
OPEB Plan
Defined Benefit Plan, Roll Forwards [Abstract]
Service cost	3	3	6	6
Interest cost	11	11	22	22
Expected return on plan assets	(29)	(25)	(58)	(51)
Amortization of:
Net loss	1	3	2	6
Prior service cost (credit)	(8)	(11)	(16)	(21)
Settlement loss	0	0	0	0
Net periodic credit	(22)	(19)	(44)	(38)
OPEB Plan | Volatility Mechanism
Amortization of:
Deferred credits			4
OPEB Plan | Consumers Energy Company
Defined Benefit Plan, Roll Forwards [Abstract]
Service cost	3	3	6	6
Interest cost	10	10	20	21
Expected return on plan assets	(27)	(24)	(54)	(48)
Amortization of:
Net loss	1	3	2	6
Prior service cost (credit)	(8)	(10)	(15)	(20)
Settlement loss	0	0	0	0
Net periodic credit	$ (21)	$ (18)	$ (41)	$ (35)