Segment Information - Revenue, Properties and Outsourcing Assets by Geographic Segment (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	$ 517.3	$ 438.8	$ 1,027.1	$ 954.2
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	201.6	174.8	436.1	390.4
United Kingdom
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	104.1	53.8	172.1	118.3
Other foreign
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	$ 211.6	$ 210.2	$ 418.9	$ 445.5