Segment Information - Property and Equipment, Net by Location (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Revenues from External Customers and Long-Lived Assets [Line Items]
Total long-lived assets	$ 1,424.4	$ 1,284.1
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Total long-lived assets	1,348.1	1,207.7
United Kingdom
Revenues from External Customers and Long-Lived Assets [Line Items]
Total long-lived assets	60.9	61.5
Other
Revenues from External Customers and Long-Lived Assets [Line Items]
Total long-lived assets	15.4	14.9
Total long-lived assets outside of the United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Total long-lived assets	$ 76.3	$ 76.4