CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY (USD $) In Thousands, unless otherwise specified	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, 2010	$ 47,872	$ 77,471	$ 97,535	$ 716	$ (13,711)	$ 209,883
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings	0	0	62,401	0	0	62,401
Other comprehensive income, net of tax	0	0	0	2,583	0	2,583
Cash dividends paid	0	0	(6,381)	0	0	(6,381)
Purchase of treasury stock	0	0	0	0	(4,136)	(4,136)
Stock-based compensation and related tax benefits	0	1,136	0	0	1,056	2,192
Stock options exercised and related tax benefits	0	634	0	0	2,263	2,897
Employee Stock Ownership Plan	0	548	0	0	1,966	2,514
Balance at Dec. 31, 2011	47,872	79,789	153,555	3,299	(12,562)	271,953
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings	0	0	41,353	0	0	41,353
Other comprehensive income, net of tax	0	0	0	580	0	580
Cash dividends paid	0	0	(8,215)	0	0	(8,215)
Purchase of treasury stock	0	0	0	0	(4,999)	(4,999)
Stock-based compensation and related tax benefits	0	584	0	0	2,010	2,594
Stock options exercised and related tax benefits	0	136	0	0	320	456
Employee Stock Ownership Plan	0	1,839	0	0	2,026	3,865
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, 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