Share-Based Compensation (Costs Associated with Share-Based Compensation Plans) (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation	$ 9.0	$ 8.7	$ 32.0	$ 52.0
RSUs
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation	6.8	6.6	25.8	45.7
PRSUs
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation	0.7	0.5	2.5	2.5
Employee Stock Purchase Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation	$ 1.5	$ 1.6	$ 3.7	$ 3.8