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Investment Securities - Net Realized and Unrealized Investment Gains (Losses) (Details) - USD ($) $ in Millions | 3 Months Ended | 6 Months Ended
--- | --- | ---
Jun. 30, 2022 | Jun. 30, 2021 | Jun. 30, 2022 | Jun. 30, 2021
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Net realized investment gains (losses) | $ (2.9) | $ 12.4 | $ 14.5 | $ 155.5
Net unrealized investment gains (losses) | (217.4) | 163.7 | (226.5) | (18.7)
Net unrealized investment gains (losses) on investment securities held at the end of the period | (113.5) | 113.0 | (94.7) | 71.3
Gain (loss) on investments, exchange rate effect | (24.5) | (0.2) | (21.8) | (0.4)
Investments Held |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Net realized and unrealized investment gains (losses) | (217.6) | 172.6 | (207.2) | 132.0
Fixed maturity investments |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Net realized investment gains (losses) | (4.8) | 0.9 | (5.9) | 2.8
Net unrealized investment gains (losses) | (54.6) | 8.2 | (134.1) | (19.2)
Short-term investments |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Net realized investment gains (losses) | (0.1) | 0.6 | (0.3) | 0.3
Net unrealized investment gains (losses) | (0.7) | 1.0 | (0.5) | 0.0
Common equity securities |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Net realized investment gains (losses) | 0.0 | 0.4 | 0.0 | 0.4
Net unrealized investment gains (losses) | (11.6) | 4.6 | (10.6) | 5.6
Net unrealized investment gains (losses) on investment securities held at the end of the period | (11.6) | 5.0 | (10.6) | 6.0
Marketing Technology (MediaAlpha) |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Net realized investment gains (losses) | 0.0 | 0.0 | 0.0 | 160.3
Net unrealized investment gains (losses) | (113.5) | 113.0 | (94.7) | (89.0)
Net unrealized investment gains (losses) on investment securities held at the end of the period | (113.5) | 113.0 | (94.7) | 71.3
Other long-term investments |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Net realized investment gains (losses) | 2.0 | 10.5 | 20.7 | (8.3)
Net unrealized investment gains (losses) | (37.0) | 36.9 | 13.4 | 83.9
Net realized and unrealized investment (losses) gains |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Net unrealized investment gains (losses) on investment securities held at the end of the period | (220.3) | 176.1 | (212.0) | 136.8
TPC Providers |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Net unrealized investment gains (losses) on investment securities held at the end of the period | 2.7 | (3.5) | 4.8 | (4.8)
Fixed maturity and short-term investments |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Net unrealized investment gains (losses) on investment securities held at the end of the period | (60.2) | 10.7 | (140.8) | (16.1)
Net realized and unrealized investment gains (losses) | (2.1) | (0.3) | (3.1) | (1.3)
Fixed maturity and short-term investments | Investments Held |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Net unrealized investment gains (losses) on investment securities held at the end of the period | (58.1) | 11.0 | (137.7) | (14.8)
Common equity securities and investment in MediaAlpha |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Net unrealized investment gains (losses) on investment securities held at the end of the period | (125.1) | 118.0 | (105.3) | 77.3
Net realized and unrealized investment gains (losses) | 0.0 | 0.0 | 0.0 | (19.9)
Common equity securities and investment in MediaAlpha | Investments Held |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Net unrealized investment gains (losses) on investment securities held at the end of the period | $ (125.1) | $ 118.0 | $ (105.3) | $ 57.4

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- Definition The net realized gain (loss) on investments sold during the period, not including gains (losses) on securities separately or otherwise categorized as trading, available-for-sale, or held-to-maturity, which, for cash flow reporting, is a component of proceeds from investing activities. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI https://asc.fasb.org/extlink&oid=126954810&loc=d3e3602-108585 + Details
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