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Contingencies And Commitments (Guarantees) (Details) $ in Millions | 12 Months Ended
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Dec. 31, 2019 USD ($) $ / MW MW | Dec. 31, 2018 USD ($) | Dec. 31, 2017 USD ($)
Guarantees |  |  |
Guarantees And Other Contingencies [Line Items] |  |  |
Expiration Date | indefinite |  |
Maximum Obligation | $ 36 |  |
Carrying Amount | $ 0 |  |
Guarantees | Consumers Energy Company |  |  |
Guarantees And Other Contingencies [Line Items] |  |  |
Expiration Date | indefinite |  |
Maximum Obligation | $ 30 |  |
Carrying Amount | $ 0 |  |
Indemnity Obligations From Stock And Asset Sales Agreements |  |  |
Guarantees And Other Contingencies [Line Items] |  |  |
Expiration Date | indefinite |  |
Maximum Obligation | $ 153 |  |
Carrying Amount | 2 |  |
Tax And Other Indemnity Obligations | Consumers Energy Company |  |  |
Guarantees And Other Contingencies [Line Items] |  |  |
Carrying Amount | 1 |  |
MCV PPA | Consumers Energy Company |  |  |
Guarantees And Other Contingencies [Line Items] |  |  |
Total | 3,295 |  |
2020 | 313 |  |
2021 | 287 |  |
2022 | 272 |  |
2023 | 225 |  |
2024 | 201 |  |
Beyond 2024 | $ 1,997 |  |
Term of unrecorded PPA | 35 years |  |
PPA minimum quantity required | MW | 1,240 |  |
PPA capacity charge per MWh (in dollars per MWh) | $ / MW | 10.14 |  |
Annual contribution to renewable resources program by counterparty | $ 5 |  |
Contract extension period | 5 years |  |
Purchases | $ 318 | $ 353 | $ 321
Palisades PPA | Consumers Energy Company |  |  |
Guarantees And Other Contingencies [Line Items] |  |  |
Total | 899 |  |
2020 | 388 |  |
2021 | 398 |  |
2022 | 113 |  |
2023 | 0 |  |
2024 | 0 |  |
Beyond 2024 | 0 |  |
Purchases | 395 | 375 | 366
Related-party PPAs | Consumers Energy Company |  |  |
Guarantees And Other Contingencies [Line Items] |  |  |
Total | 472 |  |
2020 | 71 |  |
2021 | 72 |  |
2022 | 74 |  |
2023 | 74 |  |
2024 | 75 |  |
Beyond 2024 | 106 |  |
Other PPAs | Consumers Energy Company |  |  |
Guarantees And Other Contingencies [Line Items] |  |  |
Total | 4,670 |  |
2020 | 258 |  |
2021 | 278 |  |
2022 | 291 |  |
2023 | 309 |  |
2024 | 329 |  |
Beyond 2024 | 3,205 |  |
Purchases | 336 | $ 350 | $ 349
Total PPAs | Consumers Energy Company |  |  |
Guarantees And Other Contingencies [Line Items] |  |  |
Total | 9,336 |  |
2020 | 1,030 |  |
2021 | 1,035 |  |
2022 | 750 |  |
2023 | 608 |  |
2024 | 605 |  |
Beyond 2024 | 5,308 |  |
Other |  |  |
Guarantees And Other Contingencies [Line Items] |  |  |
Total | 3,244 |  |
2020 | 1,685 |  |
2021 | 520 |  |
2022 | 451 |  |
2023 | 210 |  |
2024 | 199 |  |
Beyond 2024 | 179 |  |
Other | Consumers Energy Company |  |  |
Guarantees And Other Contingencies [Line Items] |  |  |
Total | 2,865 |  |
2020 | 1,638 |  |
2021 | 477 |  |
2022 | 413 |  |
2023 | 174 |  |
2024 | 162 |  |
Beyond 2024 | $ 1 |  |
Palisades Power Purchase Agreement | Financing Obligation | Consumers Energy Company |  |  |
Guarantees And Other Contingencies [Line Items] |  |  |
Annual average capacity (in MW) | MW | 798 |  |

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