Segment Information - Property and Equipment, Net by Location (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Revenues from External Customers and Long-Lived Assets [Line Items]
Total long-lived assets	$ 833,282	$ 812,005
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Total long-lived assets	768,572	778,157
United Kingdom
Revenues from External Customers and Long-Lived Assets [Line Items]
Total long-lived assets	57,383	30,496
Other
Revenues from External Customers and Long-Lived Assets [Line Items]
Total long-lived assets	7,327	3,352
Total revenues outside of the United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Total long-lived assets	$ 64,710	$ 33,848