Geographic Information - Property and Equipment by Geographic Area (Detail) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Revenues from External Customers and Long-Lived Assets [Line Items]
Total property and equipment, net	$ 70,295	$ 61,655
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Total property and equipment, net	48,886	46,605
India
Revenues from External Customers and Long-Lived Assets [Line Items]
Total property and equipment, net	5,641	4,176
United Kingdom
Revenues from External Customers and Long-Lived Assets [Line Items]
Total property and equipment, net	3,696	1,238
Other EMEA
Revenues from External Customers and Long-Lived Assets [Line Items]
Total property and equipment, net	7,694	5,882
Other international
Revenues from External Customers and Long-Lived Assets [Line Items]
Total property and equipment, net	$ 4,378	$ 3,754