Retirement Benefits (Schedule Of Funded Status Of Retirement Benefit Plans) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
DB Pension Plans
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation at beginning of period	$ 3,266	$ 2,973
Service cost	53	50
Interest cost	60	79
Plan amendments	0	24
Actuarial loss (gain)	(108)	355
Benefits paid	(201)	(215)
Benefit obligation at end of period	3,070	3,266	$ 2,973
Defined Benefit Plan, Roll Forwards [Abstract]
Plan assets at fair value at beginning of period	3,402	2,546
Actual return on plan assets	398	371
Company contribution	0	700
Actual benefits paid	(201)	(215)
Plan assets at fair value at end of period	3,599	3,402	2,546
Funded status	529	136
DB Pension Plans | Consumers Energy Company
Defined Benefit Plan, Roll Forwards [Abstract]
Funded status	510	138
DB SERP
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation at beginning of period	160	150
Service cost	0	0
Interest cost	3	4
Plan amendments	0	0
Actuarial loss (gain)	(4)	16
Benefits paid	(10)	(10)
Benefit obligation at end of period	149	160	150
Defined Benefit Plan, Roll Forwards [Abstract]
Plan assets at fair value at beginning of period	0	0
Actual return on plan assets	0	0
Company contribution	10	10
Actual benefits paid	(10)	(10)
Plan assets at fair value at end of period	0	0	0
Funded status	(149)	(160)
DB SERP | Consumers Energy Company
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation at beginning of period	117	109
Service cost	0	0
Interest cost	2	3
Plan amendments	0	0
Actuarial loss (gain)	(3)	12
Benefits paid	(7)	(7)
Benefit obligation at end of period	109	117	109
Defined Benefit Plan, Roll Forwards [Abstract]
Plan assets at fair value at beginning of period	0	0
Actual return on plan assets	0	0
Company contribution	7	7
Actual benefits paid	(7)	(7)
Plan assets at fair value at end of period	0	0	0
Funded status	(109)	(117)
OPEB Plan
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation at beginning of period	1,205	1,165
Service cost	18	16	14
Interest cost	23	33	41
Plan amendments	5	0
Actuarial loss (gain)	(32)	39
Benefits paid	(53)	(48)
Benefit obligation at end of period	1,166	1,205	1,165
Defined Benefit Plan, Roll Forwards [Abstract]
Plan assets at fair value at beginning of period	1,645	1,509
Actual return on plan assets	194	182
Company contribution	0	1
Actual benefits paid	(52)	(47)
Plan assets at fair value at end of period	1,787	1,645	1,509
Funded status	621	440
OPEB Plan | Consumers Energy Company
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation at beginning of period	1,158	1,120
Service cost	17	15	13
Interest cost	23	31	40
Plan amendments	5	0
Actuarial loss (gain)	(30)	37
Benefits paid	(51)	(45)
Benefit obligation at end of period	1,122	1,158	1,120
Defined Benefit Plan, Roll Forwards [Abstract]
Plan assets at fair value at beginning of period	1,535	1,410
Actual return on plan assets	182	169
Company contribution	0	1
Actual benefits paid	(49)	(45)
Plan assets at fair value at end of period	1,668	1,535	$ 1,410
Funded status	$ 546	$ 377