Derivative Financial Instruments Fair Value Hedges Carrying Amount of Hedged Assets and Liabilities and Cumulative Basis Adjustments (Details) - USD ($) $ in Millions	Jun. 30, 2025	Dec. 31, 2024
Derivative Instruments and Hedging Activities Disclosures
Hedged Asset, Statement of Financial Position [Extensible Enumeration]	Debt Securities, Available-for-Sale	Debt Securities, Available-for-Sale
Receive Fixed/Pay Fixed \| Designated as Hedging Instrument \| Fair Value Hedging
Derivative Instruments and Hedging Activities Disclosures
Hedged Asset, Fair Value Hedge	$ 668.4	$ 551.0
Receive Fixed/Pay Fixed \| Designated as Hedging Instrument \| Fair Value Hedging \| Fixed Maturity Securities
Derivative Instruments and Hedging Activities Disclosures
Hedged Asset, Fair Value Hedge, Cumulative Increase	25.8	(46.3)
hedged asset, amortized cost	$ 772.7	$ 648.4

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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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- Definition

Amount of asset hedged in fair value hedging relationship.

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Amount of cumulative increase (decrease) in fair value of hedged asset in fair value hedge, attributable to hedged risk. Excludes cumulative basis adjustment related to foreign exchange risk.

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- Definition

Indicates line item in statement of financial position that includes hedged asset.

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