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, 2012	$ 47,872	$ 82,348	$ 186,693	$ 3,879	$ (13,205)	$ 307,587
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings	0	0	51,450	0	0	51,450
Other comprehensive income (loss), net of tax	0	0	0	(2,093)	0	(2,093)
Cash dividends paid	0	0	(10,107)	0	0	(10,107)
Purchase of treasury stock	0	0	0	0	(6,864)	(6,864)
Stock-based compensation and related tax benefits	0	2,917	0	0	1,933	4,850
Stock options exercised and related tax benefits	0	84	0	0	149	233
Employee Stock Ownership Plan	0	2,214	0	0	2,162	4,376
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