Segment Information - Revenue, Properties and Outsourcing Assets by Geographic Segment (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	$ 666.2	$ 748.9	$ 1,330.7	$ 1,415.7
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	308.5	348.4	642.3	679.3
United Kingdom
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	66.6	109.3	145.5	191.3
Other foreign
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	$ 291.1	$ 291.2	$ 542.9	$ 545.1