Employee Benefit Plans - Net Gratuity Cost (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Retirement Benefits [Abstract]
Service cost	$ 487	$ 438
Interest cost	219	180
Expected return on plan assets	(142)	(124)
Amortization of actuarial (gain)/loss	(39)	(39)
Net periodic benefit cost	$ 525	$ 455