Employee Benefit Plans - Net Gratuity Cost (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Compensation and Retirement Disclosure [Abstract]
Service cost	$ 1,933	$ 1,601	$ 1,638
Interest cost	645	599	550
Expected return on plan assets	(401)	(416)	(385)
Amortization of Actuarial loss	256	90	211
Net gratuity cost	$ 2,433	$ 1,874	$ 2,014