Segment Information - Schedule of Long-lived Assets by Geographic Areas (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Segment Reporting Information [Line Items]
Property and equipment, net	$ 115,518	$ 76,276
United States
Segment Reporting Information [Line Items]
Property and equipment, net	76,791	40,550
United Kingdom
Segment Reporting Information [Line Items]
Property and equipment, net	27,454	25,287
Other foreign countries
Segment Reporting Information [Line Items]
Property and equipment, net	11,273	10,439
International
Segment Reporting Information [Line Items]
Property and equipment, net	$ 38,727	$ 35,726