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Retirement Benefits | 9 Months Ended
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Sep. 30, 2021
Defined Benefit Plan Disclosure [Line Items] |
Retirement Benefits | Retirement BenefitsCMS Energy and Consumers provide pension, OPEB, and other retirement benefits to employees under a number of different plans. Costs: Presented in the following table are the costs (credits) and other changes in plan assets and benefit obligations incurred in CMS Energy’s and Consumers’ retirement benefits plans:
In Millions
| DB Pension Plans |  | OPEB Plan
| Three Months Ended |  | Nine Months Ended |  | Three Months Ended |  | Nine Months Ended
September 30 | 2021 | 2020 |  | 2021 | 2020 |  |  | 2021 | 2020 |  | 2021 | 2020 |
CMS Energy, including Consumers |  |
Net periodic cost (credit) |  |
Service cost |  | $ | 14 |  |  | $ | 12 |  |  |  | $ | 41 |  |  | $ | 37 |  |  |  |  |  | $ | 5 |  |  | $ | 4 |  |  |  | $ | 14 |  |  | $ | 12 |  |  |
Interest cost |  | 14 |  |  | 20 |  |  |  | 44 |  |  | 61 |  |  |  |  |  | 6 |  |  | 8 |  |  |  | 17 |  |  | 25 |  |  |
Settlement loss |  | — |  |  | 1 |  |  |  | — |  |  | 1 |  |  |  |  |  | — |  |  | — |  |  |  | — |  |  | — |  |  |
Expected return on plan assets |  | (51) |  |  | (47) |  |  |  | (155) |  |  | (143) |  |  |  |  |  | (28) |  |  | (25) |  |  |  | (82) |  |  | (75) |  |  |
Amortization of: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Net loss |  | 25 |  |  | 23 |  |  |  | 76 |  |  | 67 |  |  |  |  |  | 2 |  |  | 4 |  |  |  | 6 |  |  | 11 |  |  |
Prior service cost (credit) |  | 1 |  |  | — |  |  |  | 3 |  |  | 1 |  |  |  |  |  | (14) |  |  | (14) |  |  |  | (40) |  |  | (42) |  |  |
Settlement loss |  | 1 |  |  | — |  |  |  | 4 |  |  | — |  |  |  |  |  | — |  |  | — |  |  |  | — |  |  | — |  |  |
Net periodic cost (credit) |  | $ | 4 |  |  | $ | 9 |  |  |  | $ | 13 |  |  | $ | 24 |  |  |  |  |  | $ | (29) |  |  | $ | (23) |  |  |  | $ | (85) |  |  | $ | (69) |  |  |
Consumers |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Net periodic cost (credit) |  |
Service cost |  | $ | 14 |  |  | $ | 12 |  |  |  | $ | 40 |  |  | $ | 36 |  |  |  |  |  | $ | 4 |  |  | $ | 3 |  |  |  | $ | 13 |  |  | $ | 11 |  |  |
Interest cost |  | 14 |  |  | 20 |  |  |  | 42 |  |  | 59 |  |  |  |  |  | 6 |  |  | 8 |  |  |  | 17 |  |  | 24 |  |  |
Expected return on plan assets |  | (49) |  |  | (45) |  |  |  | (147) |  |  | (136) |  |  |  |  |  | (26) |  |  | (23) |  |  |  | (77) |  |  | (70) |  |  |
Amortization of: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Net loss |  | 24 |  |  | 22 |  |  |  | 73 |  |  | 64 |  |  |  |  |  | 2 |  |  | 4 |  |  |  | 6 |  |  | 11 |  |  |
Prior service cost (credit) |  | 1 |  |  | — |  |  |  | 3 |  |  | 1 |  |  |  |  |  | (12) |  |  | (13) |  |  |  | (38) |  |  | (40) |  |  |
Settlement loss |  | 1 |  |  | — |  |  |  | 4 |  |  | — |  |  |  |  |  | — |  |  | — |  |  |  | — |  |  | — |  |  |
Net periodic cost (credit) |  | $ | 5 |  |  | $ | 9 |  |  |  | $ | 15 |  |  | $ | 24 |  |  |  |  |  | $ | (26) |  |  | $ | (21) |  |  |  | $ | (79) |  |  | $ | (64) |  |  |
Consumers Energy Company |
Defined Benefit Plan Disclosure [Line Items] |
Retirement Benefits | Retirement BenefitsCMS Energy and Consumers provide pension, OPEB, and other retirement benefits to employees under a number of different plans. Costs: Presented in the following table are the costs (credits) and other changes in plan assets and benefit obligations incurred in CMS Energy’s and Consumers’ retirement benefits plans:
In Millions
| DB Pension Plans |  | OPEB Plan
| Three Months Ended |  | Nine Months Ended |  | Three Months Ended |  | Nine Months Ended
September 30 | 2021 | 2020 |  | 2021 | 2020 |  |  | 2021 | 2020 |  | 2021 | 2020 |
CMS Energy, including Consumers |  |
Net periodic cost (credit) |  |
Service cost |  | $ | 14 |  |  | $ | 12 |  |  |  | $ | 41 |  |  | $ | 37 |  |  |  |  |  | $ | 5 |  |  | $ | 4 |  |  |  | $ | 14 |  |  | $ | 12 |  |  |
Interest cost |  | 14 |  |  | 20 |  |  |  | 44 |  |  | 61 |  |  |  |  |  | 6 |  |  | 8 |  |  |  | 17 |  |  | 25 |  |  |
Settlement loss |  | — |  |  | 1 |  |  |  | — |  |  | 1 |  |  |  |  |  | — |  |  | — |  |  |  | — |  |  | — |  |  |
Expected return on plan assets |  | (51) |  |  | (47) |  |  |  | (155) |  |  | (143) |  |  |  |  |  | (28) |  |  | (25) |  |  |  | (82) |  |  | (75) |  |  |
Amortization of: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Net loss |  | 25 |  |  | 23 |  |  |  | 76 |  |  | 67 |  |  |  |  |  | 2 |  |  | 4 |  |  |  | 6 |  |  | 11 |  |  |
Prior service cost (credit) |  | 1 |  |  | — |  |  |  | 3 |  |  | 1 |  |  |  |  |  | (14) |  |  | (14) |  |  |  | (40) |  |  | (42) |  |  |
Settlement loss |  | 1 |  |  | — |  |  |  | 4 |  |  | — |  |  |  |  |  | — |  |  | — |  |  |  | — |  |  | — |  |  |
Net periodic cost (credit) |  | $ | 4 |  |  | $ | 9 |  |  |  | $ | 13 |  |  | $ | 24 |  |  |  |  |  | $ | (29) |  |  | $ | (23) |  |  |  | $ | (85) |  |  | $ | (69) |  |  |
Consumers |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Net periodic cost (credit) |  |
Service cost |  | $ | 14 |  |  | $ | 12 |  |  |  | $ | 40 |  |  | $ | 36 |  |  |  |  |  | $ | 4 |  |  | $ | 3 |  |  |  | $ | 13 |  |  | $ | 11 |  |  |
Interest cost |  | 14 |  |  | 20 |  |  |  | 42 |  |  | 59 |  |  |  |  |  | 6 |  |  | 8 |  |  |  | 17 |  |  | 24 |  |  |
Expected return on plan assets |  | (49) |  |  | (45) |  |  |  | (147) |  |  | (136) |  |  |  |  |  | (26) |  |  | (23) |  |  |  | (77) |  |  | (70) |  |  |
Amortization of: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Net loss |  | 24 |  |  | 22 |  |  |  | 73 |  |  | 64 |  |  |  |  |  | 2 |  |  | 4 |  |  |  | 6 |  |  | 11 |  |  |
Prior service cost (credit) |  | 1 |  |  | — |  |  |  | 3 |  |  | 1 |  |  |  |  |  | (12) |  |  | (13) |  |  |  | (38) |  |  | (40) |  |  |
Settlement loss |  | 1 |  |  | — |  |  |  | 4 |  |  | — |  |  |  |  |  | — |  |  | — |  |  |  | — |  |  | — |  |  |
Net periodic cost (credit) |  | $ | 5 |  |  | $ | 9 |  |  |  | $ | 15 |  |  | $ | 24 |  |  |  |  |  | $ | (26) |  |  | $ | (21) |  |  |  | $ | (79) |  |  | $ | (64) |  |  |

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