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Investments - Summary of Proceeds and Gains (Losses) Realized on Securities (Details) - USD ($) $ in Millions | 3 Months Ended
--- | ---
Mar. 31, 2021 | Mar. 31, 2020
Fixed maturity securities |  |
Proceeds received | $ 95.5 | $ 98.2
Gross gains realized | 1.2 | 4.8
Gross losses realized | (3.4) | (0.3)
Equity Securities, FV-NI, Realized Gain (Loss) [Abstract] |  |
Proceeds received | 0.4 | 1.5
Gross gains realized | 0.1 | 0.3
Gross losses realized | $ 0.0 | $ (0.6)

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- Definition Amount of realized gain on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 9 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=121645371&loc=d3e27357-111563 + Details
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