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Contingencies and Commitments (Contingencies And Commitments) (Details) $ in Millions | 1 Months Ended | 3 Months Ended | 12 Months Ended | 24 Months Ended
--- | --- | --- | --- | ---
Sep. 30, 2020 USD ($) | Mar. 31, 2022 USD ($) site | Mar. 31, 2021 USD ($) | Dec. 31, 2021 USD ($) | Dec. 31, 2021 USD ($)
Loss Contingencies [Line Items] |  |  |  |  |
Regulatory assets |  | $ 2,138 |  | $ 2,259 | $ 2,259
Operating Revenue |  | 2,374 | $ 2,013 |  |
Consumers Energy Company |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |
Regulatory assets |  | 2,138 |  | 2,259 | 2,259
Cost of gas sold |  | 465 | 278 |  |
Maintenance and other operating expenses |  | (313) | (292) |  |
Operating Revenue |  | 2,283 | $ 1,937 |  |
Consumers Energy Company | Tax And Other Indemnity Obligations |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |
Carrying value of indemnity obligations |  | 1 |  |  |
Consumers Energy Company | Manufactured Gas Plant |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |
Regulatory assets |  | 109 |  |  |
Bay Harbor |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |
Accrual for environmental loss contingencies |  | $ 45 |  |  |
Discounted projected costs rate |  | 4.34% |  |  |
Accrual for environmental loss contingencies, inflation rate |  | 1.00% |  |  |
Remaining undiscounted obligation amount |  | $ 56 |  |  |
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 |  |  |
Manufactured Gas Plant | Consumers Energy Company |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |
Accrual for environmental loss contingencies |  | $ 57 |  |  |
Discounted projected costs rate |  | 2.57% |  |  |
Accrual for environmental loss contingencies, inflation rate |  | 2.50% |  |  |
Remaining undiscounted obligation amount |  | $ 61 |  |  |
Number of former MGPs | site |  | 23 |  |  |
Regulatory asset collection period |  | 10 years |  |  |
Electric Utility | NREPA | Consumers Energy Company |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |
Accrual for environmental loss contingencies |  | $ 2 |  |  |
Electric Utility | NREPA | Minimum | Consumers Energy Company |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |
Remediation and other response activity costs |  | 2 |  |  |
Electric Utility | NREPA | Maximum | Consumers Energy Company |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |
Remediation and other response activity costs |  | 4 |  |  |
Gas Utility | NREPA | Consumers Energy Company |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |
Accrual for environmental loss contingencies |  | 1 |  |  |
Gas Utility | NREPA | Maximum | Consumers Energy Company |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |
Accrual for environmental loss contingencies |  | 3 |  |  |
Ray Compressor Station | Consumers Energy Company |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |
Plant additions |  |  |  |  | $ 17
Insurance recoveries received |  | $ 13 |  |  |
Ray Compressor Station | Consumers Energy Company | Insurance Recoveries |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |
Reduction to plant, property and equipment |  |  |  | 6 |
Maintenance and other operating expenses |  |  |  | 3 |
Operating Revenue |  |  |  | $ 4 |
Ray Compressor Station | Consumers Energy Company | GCR underrecoveries |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |
Cost of gas sold | $ 7 |  |  |  |

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