Interest and Other Nonoperating Income (Expense) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Interest and Other Income [Abstract]
Interest income	$ 36.3	$ 23.6	$ 12.1
Retirement benefit cost other than service cost	(0.5)	(16.7)	(38.7)
Foreign currency transaction gains (losses)	(1.1)	2.4	0.4
Non-income taxes on intercompany billings	(2.6)	(2.3)	(3.9)
Argentina turnover tax	(6.8)	(1.8)	0.0
Gain (loss) on equity and debt securities	(12.8)	0.0	16.0
G4S indemnification asset adjustment	0.0	0.0	2.7
Other	1.9	(1.5)	4.4
Interest and other nonoperating income (expense)	$ 14.4	$ 3.7	$ (7.0)