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v3.25.3

Contingencies and Commitments (Narrative) (Details) $ in Millions | 9 Months Ended | 12 Months Ended |
--- | --- | --- | ---
Sep. 30, 2025 USD ($) facility | Dec. 31, 2022 USD ($) | Dec. 31, 2024 USD ($)
Loss Contingencies [Line Items] |  |  |
Environmental Loss Contingency, Statement Of Financial Position, Extensible Enumeration, Not Disclosed Flag | recorded liability |  |
Regulatory assets | $ 3,545 |  | $ 3,569
Consumers Energy Company |  |  |
Loss Contingencies [Line Items] |  |  |
Regulatory assets | 3,545 |  | $ 3,569
Consumers Energy Company | MGP sites |  |  |
Loss Contingencies [Line Items] |  |  |
Regulatory assets | $ 85 |  |
Consumers Energy Company | Ludington |  |  |
Loss Contingencies [Line Items] |  |  |
Ownership share | 51.00% |  |
Consumers Energy Company | Ludington Plant Overhaul Contract Dispute |  |  |
Loss Contingencies [Line Items] |  |  |
Damages sought |  | $ 15 |
Estimate of shared costs | $ 350 |  |
Bay Harbor |  |  |
Loss Contingencies [Line Items] |  |  |
Accrual for environmental loss contingencies | $ 47 |  |
Discount rate | 4.34% |  |
Accrual for environmental loss contingencies, inflation rate | 1.00% |  |
Accrual for environmental loss contingencies, gross | $ 59 |  |
NREPA | Electric Utility | Consumers Energy Company |  |  |
Loss Contingencies [Line Items] |  |  |
Accrual for environmental loss contingencies | 4 |  |
NREPA | Minimum | Electric Utility | Consumers Energy Company |  |  |
Loss Contingencies [Line Items] |  |  |
Remediation and other response activity costs | 4 |  |
NREPA | Maximum | Electric Utility | Consumers Energy Company |  |  |
Loss Contingencies [Line Items] |  |  |
Remediation and other response activity costs | 5 |  |
CERCLA Liability | Consumers Energy Company |  |  |
Loss Contingencies [Line Items] |  |  |
Accrual for environmental loss contingencies | 3 |  |
CERCLA Liability | Minimum | Consumers Energy Company |  |  |
Loss Contingencies [Line Items] |  |  |
Remediation and other response activity costs | 3 |  |
CERCLA Liability | Maximum | Consumers Energy Company |  |  |
Loss Contingencies [Line Items] |  |  |
Remediation and other response activity costs | 8 |  |
MGP sites | Consumers Energy Company |  |  |
Loss Contingencies [Line Items] |  |  |
Accrual for environmental loss contingencies | $ 60 |  |
Number of former MGPs | facility | 23 |  |
Regulatory asset collection period | 10 years |  |

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