Segment Information - Revenue, Properties and Outsourcing Assets by Geographic Segment (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	$ 464.6	$ 461.2	$ 1,457.8	$ 1,422.9
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	217.4	208.9	630.6	643.5
United Kingdom
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	54.9	59.0	228.4	181.7
Other foreign
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	$ 192.3	$ 193.3	$ 598.8	$ 597.7