Investments - Net Investment Income (Parenthetical) (Details) - Deposit asset underlying 10% coinsurance agreement [Member] - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Schedule of Net Investment Income, Reported Amounts, by Category [Line Items]
Gains (Losses) recognized for change in fair value of deposit asset underlying the 10% coinsurance agreement	$ (3.8)	$ (2.5)	$ 2.0
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Realized Investment Gains Losses	Realized Investment Gains Losses	Realized Investment Gains Losses
Percentage of coinsurance costs	10.00%	10.00%	10.00%

Percentage of coinsurance covered costs.

No definition available.

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- Definition

Amount of gain (loss) recognized in income from asset measured at fair value on recurring basis using unobservable input (level 3).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(1)
-URI https://asc.fasb.org/extlink&oid=126976982&loc=d3e19207-110258

+ Details

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- Definition

Indicates line item in statement in which net income is reported that includes gain (loss) from asset measured at fair value using unobservable input (level 3).

+ References

+ Details

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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.

+ References

No definition available.

+ Details

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- Details

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