Consolidated Statements Of Comprehensive Income (Parenthetical) (Unaudited) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Statement of Comprehensive Income [Abstract]
Other comprehensive income/(loss), tax	$ 17.9	$ 12.1	$ 6.3	$ 50.7
Reclassifications to earnings of realized gains/(losses) on available-for-sale securities	$ 0.0	$ 0.0	$ 5.6	$ 0.0