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Nature of Business (Details) | 3 Months Ended | 12 Months Ended |
--- | --- | --- | ---
Jun. 30, 2017 USD ($) | Dec. 31, 2017 USD ($) MW | Dec. 31, 2016 USD ($) | Jun. 14, 2017 USD ($)
Power Generation Facilities |  |  |  |
Generation capacity (in MW) | MW |  | 30,000 |  |
Discontinued Operations | GenOn |  |  |  |
Power Generation Facilities |  |  |  |
Investment in GenOn recorded under cost method at fair value |  |  |  | $ 0
Loss on deconsolidation | $ 208,000,000 | $ 634,000,000 | $ 0 |

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