Employee Benefit Plans - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Compensation And Retirement Disclosure [Abstract]
Defined Benefit Plan, Sponsor Location [Extensible List]	us-gaap:ForeignPlanMember	us-gaap:ForeignPlanMember	us-gaap:ForeignPlanMember
Funding valuation period	3 years
Defined benefit plan contributions by employer	$ 887	$ 868
Defined benefit plan estimated employer contributions for 2018	900
Contribution to defined contribution plan by employer	$ 3,100	$ 2,500	$ 2,700