Segment Information - Property and Equipment, Net by Location (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Revenues from External Customers and Long-Lived Assets [Line Items]
Total long-lived assets	$ 1,284,098	$ 833,282
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Total long-lived assets	1,207,748	768,572
United Kingdom
Revenues from External Customers and Long-Lived Assets [Line Items]
Total long-lived assets	61,462	57,383
Other
Revenues from External Customers and Long-Lived Assets [Line Items]
Total long-lived assets	14,888	7,327
Total long-lived assets outside of the United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Total long-lived assets	$ 76,350	$ 64,710