Segment Information - Revenue, Properties and Outsourcing Assets by Geographic Segment (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	$ 495.2	$ 552.1	$ 1,449.4	$ 1,676.0
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	193.6	213.4	584.0	613.3
United Kingdom
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	58.6	72.4	176.9	272.0
Other foreign
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	$ 243.0	$ 266.3	$ 688.5	$ 790.7