Derivative Financial Instruments (Hedged Items In Fair Value Hedges) (Details) - USD ($) $ in Millions	Mar. 31, 2025	Dec. 31, 2024
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Carrying value of the hedged items, available for sale debt securities	$ 7,674.3	$ 7,567.3
Cumulative hedge accounting basis adjustment, available for sale debt securities	54.3	(48.7)
Carrying value of the hedged items, senior notes and long-term subordinated debt	2,551.0	2,507.5
Cumulative hedge accounting basis adjustment, senior notes and long-term subordinated debt	(194.7)	(238.0)
Hedged asset fair value hedge discontinued cumulative increase decrease	1.6	1.8
Hedged liability fair value hedge discontinued cumulative increase decrease	$ 9.7	$ 13.8