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Retirement Benefits (Quarterly Narrative) (Details) - DB Pension Plans $ in Millions | 6 Months Ended
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Jun. 30, 2022 USD ($)
Defined Benefit Plan Disclosure [Line Items] |
Settlement loss | $ 8
Increase (decrease) in non-current pension plan assets | 113
Loss to AOCI | 3
Consumers Energy Company |
Defined Benefit Plan Disclosure [Line Items] |
Increase (decrease) in non-current pension plan assets | 110
Pension Costs |
Defined Benefit Plan Disclosure [Line Items] |
Settlement loss | 8
Increase (decrease) in non-current pension plan assets | $ (110)
Pension Costs | DB Pension Plan A Settlement |
Defined Benefit Plan Disclosure [Line Items] |
Regulatory asset collection period | 8 years
Pension Costs | Consumers Energy Company |
Defined Benefit Plan Disclosure [Line Items] |
Settlement loss | $ 8
Increase (decrease) in non-current pension plan assets | $ (110)

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