Shareholders' Equity - Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Summary of the components of accumulated other comprehensive income, net of tax
Balance at beginning of period	$ 1,125.7	$ 1,084.6	$ 974.3
Balance at end of period	1,394.6	1,125.7	1,084.6
Accumulated Other Comprehensive Income (Loss)
Summary of the components of accumulated other comprehensive income, net of tax
Balance at beginning of period	14.8	(8.2)	3.7
Balance at end of period	$ 6.0	$ 14.8	$ (8.2)