Consolidated Statements of Changes in Shareholders' Equity (USD $) In Thousands	Total	Common Stock [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income [Member]
Balance, value at Dec. 31, 2010	$ 706,878	$ 576,905	$ 117,692	$ 12,281
Balance, shares at Dec. 31, 2010		39,338
Net Income	5,779		5,779
Other comprehensive income	1,924			1,924
Issuance of common stock - stock option and other plans, value	380	380
Issuance of common stock - stock option and other plans, shares		23
Issuance of common stock - restricted stock awards, net of cancelled awards, value	335	335
Issuance of common stock - restricted stock awards, net of cancelled awards, shares		122
Stock Repurchased and Retired During Period, Shares		(2)
Stock Repurchased and Retired During Period, Value	(32)	(32)
Cash dividends paid on common stock	(1,181)		(1,181)
Balance, value at Mar. 31, 2011	714,083	577,588	122,290	14,205
Balance, shares at Mar. 31, 2011		39,481
Balance, value at Dec. 31, 2011	759,338	579,136	155,069	25,133
Balance, shares at Dec. 31, 2011		39,506
Net Income	8,902		8,902
Other comprehensive income	(1,672)			(1,672)
Issuance of common stock - stock option and other plans, value	308	308
Issuance of common stock - stock option and other plans, shares		18
Issuance of common stock - restricted stock awards, net of cancelled awards, value	450	450
Issuance of common stock - restricted stock awards, net of cancelled awards, shares		146
Cash dividends paid on common stock	(14,623)		(14,623)
Balance, value at Mar. 31, 2012	$ 752,703	$ 579,894	$ 149,348	$ 23,461
Balance, shares at Mar. 31, 2012		39,670