Derivative Financial Instruments (Hedged Items In Fair Value Hedges) (Details) - USD ($) $ in Millions |
Jun. 30, 2025 |
Dec. 31, 2024 |
|---|---|---|
| Derivative Instruments and Hedging Activities Disclosure [Abstract] | ||
| Carrying value of the hedged items, available for sale debt securities | $ 7,769.9 | $ 7,567.3 |
| Cumulative hedge accounting basis adjustment, available for sale debt securities | 102.2 | (48.7) |
| Carrying value of the hedged items, senior notes and long-term subordinated debt | 2,580.8 | 2,507.5 |
| Cumulative hedge accounting basis adjustment, senior notes and long-term subordinated debt | (165.2) | (238.0) |
| Hedged asset fair value hedge discontinued cumulative increase decrease | 1.5 | 1.8 |
| Hedged liability fair value hedge discontinued cumulative increase decrease | $ 5.7 | $ 13.8 |