Condensed Consolidated Statements of Changes in Shareholders' Equity - USD ($) $ in Thousands	Common Stock 2004 Buyback Plan [Member]	Common Stock	Surplus 2004 Buyback Plan [Member]	Surplus	Retained Earnings	Accumulated Other Comprehensive Income (Loss).	2004 Buyback Plan [Member]	Total
Balance at Dec. 31, 2014		$ 60,377		$ 701,764	$ 223,156	$ (377)		$ 984,920
Balance (in shares) at Dec. 31, 2014		24,150,702
Increase (Decrease) in Stockholders' Equity
Net income					23,926			23,926
Other Comprehensive Income, net of tax effects						3,375		3,375
Total comprehensive income								27,301
Cash dividends on Series A preferred stock					(5,556)			(5,556)
Stock options exercised		$ 53		614				667
Stock options exercised (in shares)		21,000
Restricted stock awards		$ 2		(2)
Restricted stock awards (in shares)		907
Common stock repurchased		$ (40)		(941)				(981)
Common stock repurchased (in shares)		(15,850)
Share-based compensation expense				1,213				1,213
Balance at Mar. 31, 2015		$ 60,392		702,648	241,526	2,998		$ 1,007,564
Balance (in shares) at Mar. 31, 2015		24,156,759						24,156,759
Balance (in shares) Preferred Stock at Mar. 31, 2015								0
Balance at Dec. 31, 2015		$ 60,407		703,929	298,919	(3,871)		$ 1,059,384
Balance (in shares) at Dec. 31, 2015		24,162,657						24,162,657
Balance (in shares) Preferred Stock at Dec. 31, 2015								0
Increase (Decrease) in Stockholders' Equity
Net income					24,494			$ 24,494
Other Comprehensive Income, net of tax effects						7,376		7,376
Total comprehensive income								31,870
Cash dividends on Series A preferred stock					(6,771)			(6,771)
Stock options exercised		$ 46		569				615
Stock options exercised (in shares)		18,348
Restricted stock awards		$ 72		(72)
Restricted stock awards (in shares)		28,858
Stock issued pursuant to restricted stock units		$ 90		(90)
Stock issued pursuant to restricted stock units (in shares)		35,903
Common stock repurchased	$ (82)	$ (88)	$ (2,048)	(2,192)			$ (2,130)	(2,280)
Common stock repurchased (in shares)	(32,900)	(35,033)
Share-based compensation expense				1,366				1,366
Balance at Mar. 31, 2016		$ 60,445		$ 701,462	$ 316,642	$ 3,505		$ 1,082,054
Balance (in shares) at Mar. 31, 2016		24,177,833						24,177,833
Balance (in shares) Preferred Stock at Mar. 31, 2016								0