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, 2009	$ 47,872	$ 77,238	$ 80,083	$ 5,475	$ (16,790)	$ 193,878
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings	0	0	21,960	0	0	21,960
Other comprehensive income	0	0	0	(4,759)	0	(4,759)
Cash dividends paid	0	0	(4,508)	0	0	(4,508)
Adjustment to costs related to issuance of common stock	0	36	0	0	0	36
Stock-based compensation and related tax benefits	0	440	0	0	1,149	1,589
Stock options and related tax benefits	0	6	0	0	48	54
Employee Stock Ownership Plan	0	(249)	0	0	1,882	1,633
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	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 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	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 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