Consolidated Statements Of Changes In Shareholders' Equity (USD $) In Thousands, unless otherwise specified	Series C Preferred Stock [Member] Preferred Stock [Member]	Series C Preferred Stock [Member] Surplus [Member]	Series C Preferred Stock [Member]	Preferred Stock [Member] USD ($)	Common Stock [Member] USD ($)	Surplus [Member] USD ($)	Treasury Stock [Member] USD ($)	Retained Earnings [Member] USD ($)	Accumulated Other Comprehensive Income (Loss) [Member] USD ($)	Total USD ($)
Balance at Dec. 31, 2010				$ 49,640	$ 34,864	$ 965,203		$ 392,354	$ (5,512)	$ 1,436,549
Net income								16,402		16,402
Other comprehensive income, net of tax									2,053	2,053
Cash dividends declared on common stock								(3,145)		(3,145)
Dividends on preferred stock								(999)		(999)
Accretion on preferred stock				32				(32)
Common stock repurchases							(74)			(74)
Stock-based compensation						1,094				1,094
Common stock issued for:
Exercise of stock options and warrants					33	546				579
Restricted stock awards					12	(16)				(4)
Employee stock purchase plan					13	423				436
Director compensation plan					25	337				362
Balance at Mar. 31, 2011				49,672	34,947	967,587	(74)	404,580	(3,459)	1,453,253
Balance at Dec. 31, 2011				49,768	35,982	1,001,316	(112)	459,457	(2,878)	1,543,533
Net income								23,210		23,210
Other comprehensive income, net of tax									(1,952)	(1,952)
Cash dividends declared on common stock								(3,261)		(3,261)
Dividends on preferred stock								(1,212)		(1,212)
Accretion on preferred stock				34				(34)
Stock-based compensation						2,289				2,289
Issuance of preferred stock	126,500	(3,810)	122,690
Common stock issued for:
Exercise of stock options and warrants					407	7,822	(5,592)			2,637
Restricted stock awards					94	(94)	(855)			(855)
Employee stock purchase plan					17	465				482
Director compensation plan					22	338				360
Balance at Mar. 31, 2012				$ 176,302	$ 36,522	$ 1,008,326	$ (6,559)	$ 478,160	$ (4,830)	$ 1,687,921