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Contingencies And Commitments (Contingencies And Commitments) (Details) $ in Millions | 1 Months Ended | 3 Months Ended |
--- | --- | --- | ---
Jan. 31, 2019 USD ($) | Mar. 31, 2019 USD ($) site lawsuit | Dec. 31, 2018 USD ($)
Loss Contingencies [Line Items] |  |  |
Regulatory assets |  | $ 1,711 | $ 1,743
Consumers Energy Company |  |  |
Loss Contingencies [Line Items] |  |  |
Regulatory assets |  | 1,711 | $ 1,743
Bay Harbor |  |  |
Loss Contingencies [Line Items] |  |  |
Accrual for obligations for environmental remediation |  | $ 45 |
Discounted projected costs rate |  | 4.34% |
Remaining undiscounted obligation amount |  | $ 57 |
Accrual for environmental loss contingencies, inflation rate |  | 1.00% |
Electric Utility | NREPA | Consumers Energy Company |  |  |
Loss Contingencies [Line Items] |  |  |
Accrual for obligations for environmental remediation |  | $ 3 |
Electric Utility | NREPA | Minimum | Consumers Energy Company |  |  |
Loss Contingencies [Line Items] |  |  |
Remediation and other response activity costs |  | 3 |
Electric Utility | NREPA | Maximum | Consumers Energy Company |  |  |
Loss Contingencies [Line Items] |  |  |
Remediation and other response activity costs |  | 4 |
Electric Utility | CERCLA Liability | Consumers Energy Company |  |  |
Loss Contingencies [Line Items] |  |  |
Accrual for obligations for environmental remediation |  | 3 |
Electric Utility | CERCLA Liability | Minimum | Consumers Energy Company |  |  |
Loss Contingencies [Line Items] |  |  |
Remediation and other response activity costs |  | 3 |
Electric Utility | CERCLA Liability | Maximum | Consumers Energy Company |  |  |
Loss Contingencies [Line Items] |  |  |
Remediation and other response activity costs |  | 8 |
Gas Utility | NREPA | Maximum | Consumers Energy Company |  |  |
Loss Contingencies [Line Items] |  |  |
Accrual for obligations for environmental remediation |  | 1 |
Remediation and other response activity costs |  | 3 |
Gas Utility | Manufactured Gas Plant | Consumers Energy Company |  |  |
Loss Contingencies [Line Items] |  |  |
Accrual for obligations for environmental remediation |  | $ 72 |
Discounted projected costs rate |  | 2.57% |
Remaining undiscounted obligation amount |  | $ 76 |
Number of former MGPs | site |  | 23 |
Accrual for environmental loss contingencies, inflation rate |  | 2.50% |
Authorized recovery, collection period |  | 10 years |
Regulatory assets |  | $ 131 |
Equatorial Guinea Tax Claim |  |  |
Loss Contingencies [Line Items] |  |  |
Foreign government tax claim on sale |  | $ 152 |
Class Action Lawsuits |  |  |
Loss Contingencies [Line Items] |  |  |
Number of lawsuits | lawsuit |  | 4 |
Individual Lawsuits |  |  |
Loss Contingencies [Line Items] |  |  |
Number of lawsuits | lawsuit |  | 1 |
MCV PPA | Consumers Energy Company |  |  |
Loss Contingencies [Line Items] |  |  |
Foreign government tax claim on sale | $ 270 |  |
Underwater cables Straits of Mackinac | Maximum | Consumers Energy Company |  |  |
Loss Contingencies [Line Items] |  |  |
Remediation and other response activity costs |  | $ 10 |

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