Segment Information - Revenue, Properties and Outsourcing Assets by Geographic Segment (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	$ 438.8	$ 569.4	$ 954.2	$ 1,123.9
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	174.8	208.6	390.4	399.9
United Kingdom
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	53.8	104.3	118.3	199.6
Other foreign
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	$ 210.2	$ 256.5	$ 445.5	$ 524.4