CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDERS' EQUITY (Unaudited) (USD $) In Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]
Stockholders' Equity, Beginning Balance at Dec. 31, 2010	$ 268,864	$ 1,011	$ 84,889	$ 178,939	$ 4,025
Common Stock, Shares Outstanding, Beginning Balance at Dec. 31, 2010		16,172
Net income	6,800			6,800
Total other comprehensive income, net of tax	361				361
Cash dividends declared	(3,603)			(3,603)
Share-based compensation	327		327
Exercise of stock options, issuance of other compensation-related equity instruments and related tax benefit, shares		51
Exercise of stock options, issuance of other compensation-related equity instruments and related tax benefit	900	3	897
Shares issued - dividend reinvestment plan, shares		11
Shares issued - dividend reinvestment plan	236	1	235
Stockholders' Equity, Ending Balance at Mar. 31, 2011	273,885	1,015	86,348	182,136	4,386
Common Stock, Shares Outstanding, Ending Balance at Mar. 31, 2011		16,234
Stockholders' Equity, Beginning Balance at Dec. 31, 2011	281,351	1,018	88,030	194,198	(1,895)
Common Stock, Shares Outstanding, Beginning Balance at Dec. 31, 2011		16,292
Net income	8,438			8,438
Total other comprehensive income, net of tax	497				497
Cash dividends declared	(3,809)			(3,809)
Share-based compensation	412		412
Deferred compensation plan, shares		10
Deferred compensation plan	146	1	145
Exercise of stock options, issuance of other compensation-related equity instruments and related tax benefit, shares		52
Exercise of stock options, issuance of other compensation-related equity instruments and related tax benefit	900	3	897
Stockholders' Equity, Ending Balance at Mar. 31, 2012	$ 287,935	$ 1,022	$ 89,484	$ 198,827	$ (1,398)
Common Stock, Shares Outstanding, Ending Balance at Mar. 31, 2012		16,354