Property and Equipment by Geographic Area (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Revenues from External Customers and Long-Lived Assets [Line Items]
Total property and equipment, net	$ 57,902	$ 57,096
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Total property and equipment, net	44,117	45,498
India
Revenues from External Customers and Long-Lived Assets [Line Items]
Total property and equipment, net	3,708	3,704
EMEA
Revenues from External Customers and Long-Lived Assets [Line Items]
Total property and equipment, net	6,326	5,114
Other international
Revenues from External Customers and Long-Lived Assets [Line Items]
Total property and equipment, net	$ 3,751	$ 2,780