CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Common Stock [Member]	Capital In Excess of Par Value [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income [Member]	Treasury Stock [Member]	Total
Balance at Dec. 31, 2013	$ 47,872	$ 87,563	$ 228,036	$ 1,786	$ (15,825)	$ 349,432
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings	0	0	43,029	0	0	43,029
Other comprehensive income (loss), net of tax	0	0	0	(4,438)	0	(4,438)
Cash dividends paid	0	0	(11,905)	0	0	(11,905)
Purchase of treasury stock	0	0	0	0	(10,000)	(10,000)
Stock-based compensation and related tax benefits	0	3,005	0	0	3,065	6,070
Stock options exercised and related tax benefits	0	17	0	0	122	139
Employee Stock Ownership Plan	0	826	0	0	1,000	1,826
Balance at Dec. 31, 2014	47,872	91,411	259,160	(2,652)	(21,638)	374,153
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings	0	0	46,018	0	0	46,018
Other comprehensive income (loss), net of tax	0	0	0	(3,822)	0	(3,822)
Cash dividends paid	0	0	(13,697)	0	0	(13,697)
Purchase of treasury stock	0	0	0	0	(19,623)	(19,623)
Stock-based compensation and related tax benefits	0	833	0	0	5,700	6,533
Stock options exercised and related tax benefits	0	2	0	0	207	209
Employee Stock Ownership Plan	0	1,001	0	0	1,207	2,208
Balance at Dec. 31, 2015	47,872	93,247	291,481	(6,474)	(34,147)	391,979
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings	0	0	60,430	0	0	60,430
Other comprehensive income (loss), net of tax	0	0	0	(4,554)	0	(4,554)
Cash dividends paid	0	0	(15,447)	0	0	(15,447)
Purchase of treasury stock	0	0	0	0	(377)	(377)
Stock-based compensation and related tax benefits	0	3,148	0	0	3,828	6,976
Employee Stock Ownership Plan	0	455	0	0	1,566	2,021
Balance at Dec. 31, 2016	$ 47,872	$ 96,850	$ 336,464	$ (11,028)	$ (29,130)	$ 441,028