Segment and Geographical Information - Property, Plant and Equipment, Net Based On Geographical Information (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Revenues from External Customers and Long-Lived Assets [Line Items]
Property and equipment, net	$ 66,112	$ 66,757
India
Revenues from External Customers and Long-Lived Assets [Line Items]
Property and equipment, net	35,060	39,143
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Property and equipment, net	21,182	16,371
Philippines
Revenues from External Customers and Long-Lived Assets [Line Items]
Property and equipment, net	6,748	8,217
Rest of World
Revenues from External Customers and Long-Lived Assets [Line Items]
Property and equipment, net	$ 3,122	$ 3,026