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Asset Sales and Exit Activities - Narrative (Details) $ in Millions | 1 Months Ended | 3 Months Ended |
--- | --- | --- | ---
Sep. 30, 2019 USD ($) coal_fueled_electric_generating_unit | Apr. 30, 2019 USD ($) | Dec. 31, 2019 USD ($) | Oct. 24, 2019 USD ($)
DIG's High-Voltage Equipment to ITC | Disposal Group, Held-for-sale or Disposed of by Sale, Not Discontinued Operations |  |  |  |
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |  |  |  |
Gain on disposition of assets |  | $ 16 |  |
Electric Utility | Substation Transmission Assets to METC | Disposal Group, Held-for-sale or Disposed of by Sale, Not Discontinued Operations |  |  |  |
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |  |  |  |
Gain on disposition of assets | $ 34 |  |  |
Consumers Energy Company | Coal-Fueled Electric Generating Units to be Retired |  |  |  |
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |  |  |  |
Number of units | coal_fueled_electric_generating_unit | 2 |  |  |
D.E. Karn Generating Complex | Subsequent Event |  |  |  |
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |  |  |  |
Expected cost |  |  |  | $ 35
Retention and Severance Benefits | D.E. Karn Generating Complex | Forecast | Subsequent Event |  |  |  |
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |  |  |  |
Retention and severance costs |  |  | $ 6 |

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