Consolidated Statements Of Stockholders' Equity (USD $) In Thousands	Common Stock [Member]	Capital Surplus [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income [Member]	Total
Balance at beginning of period at Dec. 31, 2009	$ 15,309	$ 69,725	$ 334,693	$ 11,023
Common stock issued	66	1,354
Tax effect of stock options		340
Stock based compensation arrangements		984
Net income			32,132		32,132
Dividends on common stock			(10,896)
Common stock acquired and canceled	(16)		(589)
Other comprehensive income, net of tax				(256)	31,876
Balance at end of period at Sep. 30, 2010	15,359	72,403	355,340	10,767	453,869
Balance at beginning of period at Jun. 30, 2010	15,347	71,196	347,979	11,070
Common stock issued	28	606
Tax effect of stock options		220
Stock based compensation arrangements		381
Net income			11,787		11,787
Dividends on common stock			(3,837)
Common stock acquired and canceled	(16)		(589)
Other comprehensive income, net of tax				(303)	11,484
Balance at end of period at Sep. 30, 2010	15,359	72,403	355,340	10,767	453,869
Balance at beginning of period at Dec. 31, 2010	15,369	73,040	361,680	8,505	458,594
Common stock issued	37	722
Tax effect of stock options		187
Stock based compensation arrangements		1,017
Net income			34,023		34,023
Dividends on common stock			(11,791)
Common stock acquired and canceled	(280)		(9,772)
Other comprehensive income, net of tax				1,659	35,682
Balance at end of period at Sep. 30, 2011	15,126	74,966	374,140	10,164	474,396
Balance at beginning of period at Jun. 30, 2011	15,273	74,229	371,150	9,745
Common stock issued	16	248
Tax effect of stock options		118
Stock based compensation arrangements		371
Net income			12,553		12,553
Dividends on common stock			(4,097)
Common stock acquired and canceled	(163)		(5,466)
Other comprehensive income, net of tax				419	12,972
Balance at end of period at Sep. 30, 2011	$ 15,126	$ 74,966	$ 374,140	$ 10,164	$ 474,396