Consolidated Statements Of Comprehensive Income (Parenthetical) (Unaudited) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Statement of Comprehensive Income [Abstract]
Other comprehensive income/(loss), tax	$ 4.4	$ 17.0	$ 4.6	$ 38.2
Reclassifications to earnings of realized gains/(losses) on available-for-sale securities	$ 0.0	$ 0.0	$ 5.6	$ 0.0