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Investment Securities - Cost or Amortized Cost, Gross Unrealized Investment Gains and Losses (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2021 | Dec. 31, 2020
Common equity securities |  |
Investment securities |  |
Cost or Amortized Cost | $ 236.3 |
Gross Unrealized Gains | 16.1 |
Gross Unrealized Losses | 0.0 |
Net Foreign Currency Gains (Losses) | (1.3) |
Common equity securities, at fair value | 251.1 |
MediaAlpha |  |
Investment securities |  |
Cost or Amortized Cost | 0.0 | $ 0.0
Gross Unrealized Gains | 261.6 | 802.2
Gross Unrealized Losses | 0.0 | 0.0
Net Foreign Currency Gains (Losses) | 0.0 | 0.0
Common equity securities, at fair value | 261.6 | 802.2
Other long-term investments |  |
Investment securities |  |
Cost or Amortized Cost | 1,186.7 | 767.4
Gross Unrealized Gains | 239.0 | 95.8
Gross Unrealized Losses | (44.1) | (78.1)
Net Foreign Currency Gains (Losses) | (3.8) | 1.7
Common equity securities, at fair value | $ 1,377.8 | $ 786.8

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