Stockholders' Equity - Summary of Changes in Stockholders' Equity (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Equity [Abstract]
Beginning Balance			$ 497,911
Net Income (Loss)	$ (7,670)	$ 12,401	(18,484)	$ 19,052
Dividend payments			(8,679)
Dividends accrued for unvested restricted stock units			5
Net unrealized gains (losses) on available-for-sale securities	104	373	(3,308)	1,708
Defined benefit plan adjustments (net of tax)	5	86	67	141
Foreign currency translation adjustment	(3,424)	$ 2,619	(2,582)	3,861
Proceeds from stock option exercises			369	$ 1,722
Purchase of treasury stock			(12,774)
Adoption of new accounting standards (see Note 1)			3,499
Stock-based compensation expense			3,603
Ending Balance	$ 459,627		$ 459,627