Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Statement Of Income And Comprehensive Income [Abstract]
Net Income (Loss)	$ (10,814)	$ 6,651
Other Comprehensive Income (Loss), net of tax
Net unrealized gains (losses) on available-for-sale securities	(3,412)	1,335
Net unrealized gains (losses) on cash flow hedges		79
Defined benefit plan adjustments	62	55
Foreign currency translation	842	1,242
Other Comprehensive Income (Loss), net of tax	(2,508)	2,711
Comprehensive Income (Loss), net of tax	$ (13,322)	$ 9,362