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Contingencies and Commitments (Contingencies And Commitments) (Details) $ in Thousands | 1 Months Ended | 3 Months Ended | 26 Months Ended |
--- | --- | --- | --- | ---
Sep. 30, 2020 USD ($) | May 30, 2020 USD ($) | Mar. 31, 2021 USD ($) site | Mar. 31, 2020 USD ($) | Mar. 31, 2021 USD ($) site | Dec. 31, 2020 USD ($)
Loss Contingencies [Line Items] |  |  |  |  |  |
Regulatory assets |  |  | $ 2,613,000 |  | $ 2,613,000 | $ 2,653,000
Operating Revenue |  |  | 2,083,000 | $ 1,864,000 |  |
Consumers Energy Company |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |
Regulatory assets |  |  | 2,613,000 |  | 2,613,000 | $ 2,653,000
Cost of gas sold |  |  | 278,000 | 270,000 |  |
Maintenance and other operating expenses |  |  | (292,000) | (278,000) |  |
Operating Revenue |  |  | 1,937,000 | $ 1,744,000 |  |
Consumers Energy Company | Manufactured Gas Plant |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |
Regulatory assets |  |  | 118,000 |  | 118,000 |
Bay Harbor |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |
Accrual for environmental loss contingencies |  |  | $ 45,000 |  | $ 45,000 |
Discounted projected costs rate |  |  | 4.34% |  | 4.34% |
Accrual for environmental loss contingencies, inflation rate |  |  | 1.00% |  | 1.00% |
Remaining undiscounted obligation amount |  |  | $ 56,000 |  | $ 56,000 |
CERCLA Liability | Consumers Energy Company |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |
Accrual for environmental loss contingencies |  |  | 3,000 |  | 3,000 |
CERCLA Liability | Minimum | Consumers Energy Company |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |
Remediation and other response activity costs |  |  | 3,000 |  | 3,000 |
CERCLA Liability | Maximum | Consumers Energy Company |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |
Remediation and other response activity costs |  |  | 8,000 |  | 8,000 |
Manufactured Gas Plant | Consumers Energy Company |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |
Accrual for environmental loss contingencies |  |  | $ 56,000 |  | $ 56,000 |
Discounted projected costs rate |  |  | 2.57% |  | 2.57% |
Accrual for environmental loss contingencies, inflation rate |  |  | 2.50% |  | 2.50% |
Remaining undiscounted obligation amount |  |  | $ 61,000 |  | $ 61,000 |
Number of former MGPs | site |  |  | 23 |  | 23 |
Regulatory asset collection period |  |  | 10 years |  |  |
Electric Utility | NREPA | Consumers Energy Company |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |
Accrual for environmental loss contingencies |  |  | $ 2,000 |  | $ 2,000 |
Electric Utility | NREPA | Minimum | Consumers Energy Company |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |
Remediation and other response activity costs |  |  | 2,000 |  | 2,000 |
Electric Utility | NREPA | Maximum | Consumers Energy Company |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |
Remediation and other response activity costs |  |  | 4,000 |  | 4,000 |
Gas Utility | NREPA | Consumers Energy Company |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |
Accrual for environmental loss contingencies |  |  | 1,000 |  | 1,000 |
Gas Utility | NREPA | Maximum | Consumers Energy Company |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |
Accrual for environmental loss contingencies |  |  | 3,000 |  | 3,000 |
Equatorial Guinea Tax Claim |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |
Foreign government tax claim on sale |  |  | 152,000 |  | 152,000 |
Civil Case, Consumers V. MPSC Staff | Consumers Energy Company |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |
Civil penalty |  | $ 10 |  |  |  |
Ray Compressor Station | Consumers Energy Company |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |
Plant additions |  |  |  |  | 17,000 |
Insurance recoveries |  |  | 10,000 |  | 10,000 |
Ray Compressor Station | Consumers Energy Company | Repair Costs |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |
Insurance recoveries |  |  | 7,000 |  | 7,000 |
Ray Compressor Station | Consumers Energy Company | Incremental Gas Purchases |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |
Insurance recoveries |  |  | 3,000 |  | $ 3,000 |
Ray Compressor Station | Consumers Energy Company | Insurance Recoveries |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |
Reduction to plant, property and equipment |  |  | 4,000 |  |  |
Maintenance and other operating expenses |  |  | 3,000 |  |  |
Operating Revenue |  |  | $ 3,000 |  |  |
Ray Compressor Station | Consumers Energy Company | GCR underrecoveries |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |
Cost of gas sold | $ 7,000 |  |  |  |  |

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