Defined Benefit Plans (Schedule of Korea Defined Benefit Plan Net Cost) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 309	$ 251
Interest cost	58	59
Net pension cost	69	90
Korea Defined Benefit Plan
Defined Benefit Plan Disclosure [Line Items]
Service cost	145	134	$ 446	$ 221
Interest cost	23	20	82	34
Net pension cost	168	154	528	255
Cost recognized as a component of compensation cost | Korea Defined Benefit Plan
Defined Benefit Plan Disclosure [Line Items]
Net pension cost	145	134	446	221
Net cost recognized in other components of defined benefit plans, net | Korea Defined Benefit Plan
Defined Benefit Plan Disclosure [Line Items]
Net pension cost	$ 23	$ 20	$ 82	$ 34