Interim Condensed Consolidated Statements of Stockholders' Equity (Unaudited) - 9 months ended Sep. 30, 2017 - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Treasury Stock	Retained Earnings	Accumulated Other Comprehensive Loss
Balance at Dec. 31, 2016	$ 387,717	$ 1,146	$ 99,765	$ (426)	$ 334,988	$ (47,756)
Balance (shares) at Dec. 31, 2016		11,420
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	41,075				41,075
Adoption of new accounting standard	(166)		(166)
Adoption of new accounting standard | Adoption of new accounting standard			11		(11)
Translation adjustment	17,596					17,596
Net actuarial gain arising during period	413					413
Stock-based compensation	1,254		1,254
Exercise of stock options	2,059	$ 10	2,049
Exercise of stock options (shares)		102
Redemptions of common stock to satisfy withholding taxes related to stock-based compensation	(166)		(166)
Redemptions of common stock to satisfy withholding taxes related to stock-based compensation | Adoption of new accounting standard			11		(11)
Dividends paid ($.30 per share)	(3,455)				(3,455)
Balance at Sep. 30, 2017	$ 446,493	$ 1,156	$ 102,913	$ (426)	$ 372,597	$ (29,747)
Balance (shares) at Sep. 30, 2017		11,522