Investments - Net Realized Gains on Sales of Investments (Details) - Fixed Maturities - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2020	Mar. 31, 2019
Net Investment Income [Line Items]
Gains on Sales	$ 15.9	$ 15.1
Losses on Sales	$ (1.1)	$ (2.6)

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).

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=118939692&loc=d3e27357-111563

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Amount of realized loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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