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Derivative Financial Instruments Fair Value Hedges Carrying Amount of Hedged Assets and Liabilities and Cumulative Basis Adjustments (Details) - Interest Rate Swaps - Receive Fixed/Pay Fixed - Designated as Hedging Instrument - Fair Value Hedging - USD ($) $ in Millions | Jun. 30, 2024 | Dec. 31, 2023
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Derivative Instruments and Hedging Activities Disclosures |  |
Hedged Asset, Statement of Financial Position [Extensible Enumeration] | Fixed Maturity Securities - at fair value (amortized cost of $38,554.3; $38,410.6; allowance for credit losses of $5.1; $2.2) | Fixed Maturity Securities - at fair value (amortized cost of $38,554.3; $38,410.6; allowance for credit losses of $5.1; $2.2)
Hedged Asset, Fair Value Hedge | $ 549.4 | $ 529.2
Fixed Maturity Securities |  |
Derivative Instruments and Hedging Activities Disclosures |  |
Hedged Asset, Fair Value Hedge, Cumulative Increase | $ (25.6) | $ (6.1)

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