Retirement Benefits (Schedule Of Net Benefit Costs) (Details) - USD ($)
$ in Millions |
3 Months Ended |
Mar. 31, 2020 |
Mar. 31, 2019 |
| DB Pension Plans |
|
|
| Net periodic cost (credit) |
|
|
| Service cost |
$ 12
|
$ 10
|
| Interest cost |
21
|
25
|
| Expected return on plan assets |
(48)
|
(40)
|
| Amortization of: |
|
|
| Net loss |
22
|
12
|
| Prior service credit |
0
|
0
|
| Net periodic cost (credit) |
7
|
7
|
| DB Pension Plans | Consumers Energy Company |
|
|
| Net periodic cost (credit) |
|
|
| Service cost |
12
|
10
|
| Interest cost |
20
|
23
|
| Expected return on plan assets |
(45)
|
(38)
|
| Amortization of: |
|
|
| Net loss |
21
|
12
|
| Prior service credit |
0
|
0
|
| Net periodic cost (credit) |
8
|
7
|
| OPEB Plan |
|
|
| Net periodic cost (credit) |
|
|
| Service cost |
4
|
4
|
| Interest cost |
8
|
10
|
| Expected return on plan assets |
(25)
|
(22)
|
| Amortization of: |
|
|
| Net loss |
4
|
7
|
| Prior service credit |
(14)
|
(16)
|
| Net periodic cost (credit) |
(23)
|
(17)
|
| OPEB Plan | Consumers Energy Company |
|
|
| Net periodic cost (credit) |
|
|
| Service cost |
4
|
3
|
| Interest cost |
8
|
10
|
| Expected return on plan assets |
(23)
|
(21)
|
| Amortization of: |
|
|
| Net loss |
4
|
7
|
| Prior service credit |
(14)
|
(15)
|
| Net periodic cost (credit) |
$ (21)
|
$ (16)
|