Consolidated Statements Of Changes In Shareholders Equity (Unaudited) (USD $) In Thousands, unless otherwise specified	Total	Series C Preferred Stock [Member]	Series A Preferred Stock [Member]	Preferred stock	Preferred stock Series C Preferred Stock [Member]	Preferred stock Series A Preferred Stock [Member]	Common stock	Common stock Series C Preferred Stock [Member]	Common stock Series A Preferred Stock [Member]	Surplus	Surplus Series C Preferred Stock [Member]	Surplus Series A Preferred Stock [Member]	Treasury stock	Treasury stock Series C Preferred Stock [Member]	Treasury stock Series A Preferred Stock [Member]	Retained earnings	Retained earnings Series C Preferred Stock [Member]	Retained earnings Series A Preferred Stock [Member]	Accumulated other comprehensive income (loss)	Accumulated other comprehensive income (loss) Series C Preferred Stock [Member]	Accumulated other comprehensive income (loss) Series A 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	81,107															81,107
Other comprehensive (loss) income, net of tax	12,683																		12,683
Cash dividends declared on common stock	(6,537)															(6,537)
Dividends on preferred stock	(6,374)															(6,374)
Accretion on preferred stock	0			103												(103)
Stock-based compensation	7,260									7,260			0
Issuance of Series C preferred stock		122,690			126,500			0			(3,810)			0			0			0
Common stock issued for:
Acquisitions	894			0			26			868			0			0			0
Exercise of stock options and warrants	4,098						439			10,050			(6,391)
Restricted stock awards	(1,016)						123			(152)			(987)
Employee stock purchase plan	1,832						55			1,777
Director compensation plan	1,130						22			1,108
Balance at Sep. 30, 2012	1,761,300			176,371			36,647			1,018,417			(7,490)			527,550			9,805
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	101,922															101,922			0
Other comprehensive (loss) income, net of tax	(54,125)																		(54,125)
Cash dividends declared on common stock	(6,903)															(6,903)
Dividends on preferred stock	(6,744)															(6,744)
Accretion on preferred stock	0			70												(70)
Conversion of Series A preferred stock to common stock			0			(49,976)			1,944			48,032			0			0			0
Stock-based compensation	6,598									6,598
Common stock issued for:
Acquisitions	23,070			0			648			22,422			0			0			0
Exercise of stock options and warrants	2,026						79			2,161			(214)
Restricted stock awards	37						135			140			(238)
Employee stock purchase plan	1,848						47			1,801
Director compensation plan	1,132						31			1,101
Balance at Sep. 30, 2013	$ 1,873,566			$ 126,500			$ 39,992			$ 1,118,550			$ (8,290)			$ 643,228			$ (46,414)