Defined Benefit Plans (Schedule of Korea Defined Benefit Plan Net Cost) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 309	$ 245
Interest cost	58	57
Net pension cost	69	89
Korea Defined Benefit Plan
Defined Benefit Plan Disclosure [Line Items]
Service cost	150	88	$ 301	$ 88
Interest cost	29	13	58	13
Net pension cost	179	101	359	101
Cost recognized as a component of compensation cost | Korea Defined Benefit Plan
Defined Benefit Plan Disclosure [Line Items]
Net pension cost	150	88	301	88
Net cost recognized in other components of defined benefit plans, net | Korea Defined Benefit Plan
Defined Benefit Plan Disclosure [Line Items]
Net pension cost	$ 29	$ 13	$ 58	$ 13