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Investments in Unconsolidated Entities - Narrative (Details) - USD ($) $ in Millions | 3 Months Ended | 4 Months Ended | 6 Months Ended |  |
--- | --- | --- | --- | --- | ---
Jun. 30, 2019 | Jun. 30, 2018 | Jun. 30, 2019 | Jun. 30, 2019 | Jun. 30, 2018 | Feb. 26, 2019 | Dec. 31, 2018
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |
Total revenues | $ 129.0 | $ 122.3 |  | $ 562.6 | $ 164.4 |  |
Total assets | 3,752.2 |  | $ 3,752.2 | 3,752.2 |  |  | $ 3,362.6
Total liabilities | 744.3 |  | 744.3 | 744.3 |  |  | 644.4
MediaAlpha |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |
Ownership interest (as a percent) |  |  |  |  |  | 48.30% |
Fully diluted ownership interest (as a percent) |  |  |  |  |  | 42.00% |
Assets, fair value | 114.7 |  | 114.7 | 114.7 |  |  |
Unrealized investment gain |  |  |  | 114.7 |  |  |
Total assets | 0.0 |  | 0.0 | 0.0 |  |  | 88.4
Total liabilities | 0.0 |  | 0.0 | 0.0 |  |  | $ 46.9
MediaAlpha |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |
Total revenues | 0.0 | $ 71.8 |  | 48.8 | $ 143.5 |  |
MediaAlpha | MediaAlpha |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |
Total revenues | 89.1 |  | 122.7 |  |  |  |
Expenses | 83.3 |  | 115.8 |  |  |  |
Pre-tax income | 5.8 |  | 6.9 |  |  |  |
Total assets | 107.4 |  | 107.4 | 107.4 |  |  |
Total liabilities | $ 152.9 |  | $ 152.9 | $ 152.9 |  |  |

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