Consolidated Statements of Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Treasury Stock	Retained Earnings	Accumulated Other Comprehensive Income
Balance (in shares) at Dec. 31, 2014		11,264
Balance at Dec. 31, 2014	$ 337,670	$ 1,130	$ 93,849	$ (426)	$ 259,476	$ (16,359)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	43,209				43,209
Translation adjustment	(20,112)					(20,112)
Net actuarial gain (loss) arising during period net of taxes	392					392
Tax effect of exercised non-qualified stock options	(142)		(142)
Stock-based compensation	1,057		1,057
Exercise of stock options (in shares)		86
Exercise of stock options	2,023	$ 9	2,014
Dividends paid	(3,628)				(3,628)
Balance (in shares) at Dec. 31, 2015		11,350
Balance at Dec. 31, 2015	360,469	$ 1,139	96,778	(426)	299,057	(36,079)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	40,045				40,045
Translation adjustment	(13,156)					(13,156)
Net actuarial gain (loss) arising during period net of taxes	1,479					1,479
Tax effect of exercised non-qualified stock options	230		230
Stock-based compensation	1,414		1,414
Exercise of stock options (in shares)		70
Exercise of stock options	1,369	$ 7	1,362
Repurchased shares	(19)		(19)	0
Dividends paid	(4,114)				(4,114)
Balance (in shares) at Dec. 31, 2016		11,420
Balance at Dec. 31, 2016	387,717	$ 1,146	99,765	(426)	334,988	(47,756)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	44,315				44,315
Translation adjustment	16,966					16,966
Net actuarial gain (loss) arising during period net of taxes	624					624
Stock-based compensation	1,869		1,869
Exercise of stock options (in shares)		114
Exercise of stock options	2,397	$ 12	2,385
Repurchased shares	(166)		(166)
Other	0		11		(11)
Dividends paid	(4,614)				(4,614)
Balance (in shares) at Dec. 31, 2017		11,534
Balance at Dec. 31, 2017	$ 449,108	$ 1,158	$ 103,864	$ (426)	$ 374,678	$ (30,166)