Marketable Securities and Fair Value Measurements (Details) - Level 2 - Fair Value, Measurements, Recurring - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost	$ 1,085.7	$ 952.4
Gross Unrealized Gains	0.3	1.5
Gross Unrealized Losses	(4.7)	(4.6)
Fair Value	1,081.3	949.3
Corporate bonds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost	1,074.5	934.4
Gross Unrealized Gains	0.3	1.5
Gross Unrealized Losses	(4.7)	(4.6)
Fair Value	1,070.1	931.3
Government securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost	11.2	18.0
Gross Unrealized Gains	0.0	0.0
Gross Unrealized Losses	0.0	0.0
Fair Value	$ 11.2	$ 18.0