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, 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
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	497				497
Total other comprehensive income (loss), net of tax	497
Cash dividends declared	(3,809)			(3,809)
Share-based compensation	412		412
Exercise of stock options, issuance of other compensation-related equity instruments and related tax benefit, shares		10
Exercise of stock options, issuance of other compensation-related equity instruments and related tax benefit	146	1	145
Shares issued - dividend reinvestment plan, shares		52
Shares issued - dividend reinvestment plan	900	3	897
Stockholders' Equity, Ending Balance at Mar. 31, 2012	287,935	1,022		198,827	(1,398)
Common Stock, Shares Outstanding, Ending Balance at Mar. 31, 2012		16,354
Stockholders' Equity, Beginning Balance at Dec. 31, 2012	295,652	1,024	91,453	213,674	(10,499)
Common Stock, Shares Outstanding, Beginning Balance at Dec. 31, 2012		16,380
Net income	7,421			7,421
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	1,181				1,181
Total other comprehensive income (loss), net of tax	1,181
Cash dividends declared	(4,175)			(4,175)
Share-based compensation	581		581
Deferred compensation plan, shares		2
Deferred compensation plan	30	0	30
Exercise of stock options, issuance of other compensation-related equity instruments and related tax benefit, shares		38
Exercise of stock options, issuance of other compensation-related equity instruments and related tax benefit	631	3	628
Shares issued - dividend reinvestment plan, shares		5
Shares issued - dividend reinvestment plan	(30)	0	(30)
Stockholders' Equity, Ending Balance at Mar. 31, 2013	$ 301,291	$ 1,027	$ 92,662	$ 216,920	$ (9,318)
Common Stock, Shares Outstanding, Ending Balance at Mar. 31, 2013		16,425