Derivative Financial Instruments (Hedged Items In Fair Value Hedges) (Details) - USD ($)	Mar. 31, 2024	Dec. 31, 2023
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Carrying value of the hedged items, available for sale debt securities	$ 7,319,000,000	$ 5,048,800,000
Cumulative hedge accounting basis adjustment, available for sale debt securities	(45,500,000)	77,500,000
Carrying value of the hedged items, senior notes and long-term subordinated debt	2,469,900,000	2,495,900,000
Cumulative hedge accounting basis adjustment, senior notes and long-term subordinated debt	(274,800,000)	(248,700,000)
Hedged asset fair value hedge discontinued cumulative increase decrease	2,100,000	2,200,000
Hedged liability fair value hedge discontinued cumulative increase decrease	$ 25,600,000	$ 29,600,000