Consolidated Statements Of Changes In Shareholders Equity (Unaudited) (USD $) In Thousands, unless otherwise specified	Total	Series C Preferred Stock [Member]	Preferred stock	Preferred stock Series C Preferred Stock [Member]	Common stock	Common stock Series C Preferred Stock [Member]	Surplus	Surplus Series C Preferred Stock [Member]	Treasury stock	Treasury stock Series C Preferred Stock [Member]	Retained earnings	Retained earnings Series C Preferred Stock [Member]	Accumulated other comprehensive income (loss)	Accumulated other comprehensive income (loss) Series C Preferred Stock [Member]
Balance at Dec. 31, 2011	$ 1,543,533		$ 49,768		$ 35,982		$ 1,001,316		$ (112)		$ 459,457		$ (2,878)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	23,210										23,210
Other comprehensive loss, 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	0		34								(34)
Stock-based compensation	(2,289)						2,289		0
Issuance of Series C preferred stock		122,690		126,500		0		(3,810)		0		0		0
Common stock issued for:
Exercise of stock options and warrants	2,637				407		7,822		(5,592)
Restricted stock awards	(855)				94		(94)		(855)
Employee stock purchase plan	482				17		465
Director compensation plan	360				22		338
Balance at Mar. 31, 2012	1,687,921		176,302		36,522		1,008,326		(6,559)		478,160		(4,830)
Balance at Dec. 31, 2012	1,804,705		176,406		37,108		1,036,295		(7,838)		555,023		7,711
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	32,052										32,052		0
Other comprehensive loss, net of tax	(8,778)												(8,778)
Cash dividends declared on common stock	(3,328)										(3,328)
Dividends on preferred stock	(2,581)										(2,581)
Accretion on preferred stock	0		35								(35)
Stock-based compensation	2,413						2,413
Common stock issued for:
Exercise of stock options and warrants	115				9		320		(214)
Restricted stock awards	66				111		90		(135)
Employee stock purchase plan	641				13		628
Director compensation plan	383				31		352
Balance at Mar. 31, 2013	$ 1,825,688		$ 176,441		$ 37,272		$ 1,040,098		$ (8,187)		$ 581,131		$ (1,067)