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Location and Fair Values of Derivative Financial Instruments (Detail) - USD ($) $ in Millions | Sep. 30, 2025 | Dec. 31, 2024
--- | --- | ---
Derivative |  |
Derivative, Notional Amount | $ 3,851.1 | $ 3,751.4
Other Long-term Investments |  |
Derivative |  |
Asset Derivatives Fair Value | 70.5 | 90.9
Other Liabilities |  |
Derivative |  |
Liability Derivatives Fair Value | 259.6 | 255.7
Designated as Hedging Instrument |  |
Derivative |  |
Derivative, Notional Amount | 3,532.3 | 3,445.5
Designated as Hedging Instrument | Cash Flow Hedging |  |
Derivative |  |
Derivative, Notional Amount | 2,763.6 | 2,709.1
Designated as Hedging Instrument | Forward Benchmark Interest Rate Lock | Cash Flow Hedging |  |
Derivative |  |
Derivative, Notional Amount | 2,634.0 | 2,570.0
Designated as Hedging Instrument | Interest Rate Swaps | Cash Flow Hedging |  |
Derivative |  |
Derivative, Notional Amount | 129.6 | 139.1
Designated as Hedging Instrument | Interest Rate Swaps | Fair Value Hedging |  |
Derivative |  |
Derivative, Notional Amount | 768.7 | 736.4
Designated as Hedging Instrument | Other Long-term Investments |  |
Derivative |  |
Asset Derivatives Fair Value | 56.3 | 75.7
Designated as Hedging Instrument | Other Long-term Investments | Cash Flow Hedging |  |
Derivative |  |
Asset Derivatives Fair Value | 20.8 | 21.0
Designated as Hedging Instrument | Other Long-term Investments | Forward Benchmark Interest Rate Lock | Cash Flow Hedging |  |
Derivative |  |
Asset Derivatives Fair Value | 5.0 | 3.4
Designated as Hedging Instrument | Other Long-term Investments | Interest Rate Swaps | Cash Flow Hedging |  |
Derivative |  |
Asset Derivatives Fair Value | 15.8 | 17.6
Designated as Hedging Instrument | Other Long-term Investments | Interest Rate Swaps | Fair Value Hedging |  |
Derivative |  |
Asset Derivatives Fair Value | 35.5 | 54.7
Designated as Hedging Instrument | Other Liabilities |  |
Derivative |  |
Liability Derivatives Fair Value | 242.8 | 239.3
Designated as Hedging Instrument | Other Liabilities | Cash Flow Hedging |  |
Derivative |  |
Liability Derivatives Fair Value | 208.5 | 224.3
Designated as Hedging Instrument | Other Liabilities | Forward Benchmark Interest Rate Lock | Cash Flow Hedging |  |
Derivative |  |
Liability Derivatives Fair Value | 207.1 | 223.2
Designated as Hedging Instrument | Other Liabilities | Interest Rate Swaps | Cash Flow Hedging |  |
Derivative |  |
Liability Derivatives Fair Value | 1.4 | 1.1
Designated as Hedging Instrument | Other Liabilities | Interest Rate Swaps | Fair Value Hedging |  |
Derivative |  |
Liability Derivatives Fair Value | 34.3 | 15.0
Not Designated as Hedging Instrument |  |
Derivative |  |
Derivative, Notional Amount | 318.8 | 305.9
Not Designated as Hedging Instrument | Interest Rate Swaps |  |
Derivative |  |
Derivative, Notional Amount | 119.7 | 125.9
Not Designated as Hedging Instrument | Foreign Exchange Forward |  |
Derivative |  |
Derivative, Notional Amount | 49.1 | 51.1
Not Designated as Hedging Instrument | Total Return Swap |  |
Derivative |  |
Derivative, Notional Amount | 150.0 | 128.9
Not Designated as Hedging Instrument | Embedded Derivative in Modified Coinsurance Arrangement |  |
Derivative |  |
Derivative, Notional Amount | 0.0 | 0.0
Not Designated as Hedging Instrument | Other Long-term Investments |  |
Derivative |  |
Asset Derivatives Fair Value | 14.2 | 15.2
Not Designated as Hedging Instrument | Other Long-term Investments | Interest Rate Swaps |  |
Derivative |  |
Asset Derivatives Fair Value | 0.3 | 0.6
Not Designated as Hedging Instrument | Other Long-term Investments | Foreign Exchange Forward |  |
Derivative |  |
Asset Derivatives Fair Value | 0.0 | 3.1
Not Designated as Hedging Instrument | Other Long-term Investments | Total Return Swap |  |
Derivative |  |
Asset Derivatives Fair Value | 0.0 | 0.0
Not Designated as Hedging Instrument | Other Long-term Investments | Embedded Derivative in Modified Coinsurance Arrangement |  |
Derivative |  |
Asset Derivatives Fair Value | 13.9 | 11.5
Not Designated as Hedging Instrument | Other Liabilities |  |
Derivative |  |
Liability Derivatives Fair Value | 16.8 | 16.4
Not Designated as Hedging Instrument | Other Liabilities | Interest Rate Swaps |  |
Derivative |  |
Liability Derivatives Fair Value | 15.7 | 16.4
Not Designated as Hedging Instrument | Other Liabilities | Foreign Exchange Forward |  |
Derivative |  |
Liability Derivatives Fair Value | 1.1 | 0.0
Not Designated as Hedging Instrument | Other Liabilities | Total Return Swap |  |
Derivative |  |
Liability Derivatives Fair Value | 0.0 | 0.0
Not Designated as Hedging Instrument | Other Liabilities | Embedded Derivative in Modified Coinsurance Arrangement |  |
Derivative |  |
Liability Derivatives Fair Value | $ 0.0 | $ 0.0

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