Segment Information - Property and Equipment, Net by Location (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Revenues from External Customers and Long-Lived Assets [Line Items]
Total property and equipment, net	$ 698,362	$ 697,715
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Total property and equipment, net	665,552	661,421
United Kingdom
Revenues from External Customers and Long-Lived Assets [Line Items]
Total property and equipment, net	26,921	32,793
Other
Revenues from External Customers and Long-Lived Assets [Line Items]
Total property and equipment, net	5,889	3,501
Total revenues outside of the United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Total property and equipment, net	$ 32,810	$ 36,294