CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY (Unaudited) - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Capital in Excess of Par Value	Retained Earnings	Accumulated Other Comprehensive Loss	Treasury Stock
Balance at beginning of period (shares) at Dec. 31, 2017		25,018
Balance at beginning of period at Dec. 31, 2017	$ 353,396	$ 250	$ 88,006	$ 374,783	$ (20,148)	$ (89,495)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	11,054			11,054
Other comprehensive loss, net of tax	2,845				2,845
Stock repurchased	(823)					(823)
Stock issued (canceled) under employee plans (shares)		50
Stock issued (canceled) under employee plans	667	$ 1	666
Stock-based compensation expense	1,096		1,096
Balance at end of period (shares) at Mar. 31, 2018		25,068
Balance at end of period at Mar. 31, 2018	369,833	$ 251	89,768	387,435	(17,303)	(90,318)
Balance at beginning of period (shares) at Dec. 31, 2018		25,254
Balance at beginning of period at Dec. 31, 2018	369,275	$ 253	90,851	411,325	(42,685)	(90,469)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	3,890			3,890
Other comprehensive loss, net of tax	(587)				(587)
Stock repurchased	(42)					(42)
Stock issued (canceled) under employee plans (shares)		(26)
Stock issued (canceled) under employee plans	(1)	$ (1)
Stock-based compensation expense	862		862
Balance at end of period (shares) at Mar. 31, 2019		25,228
Balance at end of period at Mar. 31, 2019	$ 373,214	$ 252	$ 91,713	$ 415,032	$ (43,272)	$ (90,511)