Employee Benefit Plans - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Employee contribution amount	$ 18,000
Defined Benefit Plan, contributions by employer	0
Expected amortization out of comprehensive income	$ 30,000
Maximum
Defined Benefit Plan Disclosure [Line Items]
Employee contribution percentage	60.00%
Provident Fund
Defined Benefit Plan Disclosure [Line Items]
Contribution expense recognized by Indian entities	$ 5,700,000	$ 5,900,000	$ 6,500,000
Gratuity Plan
Defined Benefit Plan Disclosure [Line Items]
Contribution expense recognized by Indian entities	3,800,000	3,500,000	$ 3,700,000
Accrued liability for retirement plan	$ 15,300,000	$ 13,600,000