Consolidated Statements Of Changes In Shareholders Equity (Unaudited) - USD ($) $ in Thousands	Total	Preferred stock	Common stock	Surplus	Treasury stock	Retained earnings	Accumulated other comprehensive loss
Balance at Dec. 31, 2013	$ 1,900,589	$ 126,477	$ 46,181	$ 1,117,032	$ (3,000)	$ 676,935	$ (63,036)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	73,041					73,041
Other comprehensive income (loss), net of tax	28,533						28,533
Cash dividends declared on common stock	(9,272)					(9,272)
Dividends on preferred stock	(3,162)					(3,162)
Stock-based compensation	3,754			3,754	0
Conversion of Series C preferred stock to common stock	0	(10)	1	9
Common stock issued for:
Exercise of stock options and warrants	2,506		347	2,472	(313)
Restricted stock awards	39		48	127	(136)
Employee stock purchase plan	1,424		30	1,394
Director compensation plan	783		20	763
Balance at Jun. 30, 2014	1,998,235	126,467	46,627	1,125,551	(3,449)	737,542	(34,503)
Balance at Dec. 31, 2014	2,069,822	126,467	46,881	1,133,955	(3,549)	803,400	(37,332)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	82,883					82,883	0
Other comprehensive income (loss), net of tax	(24,539)						(24,539)
Cash dividends declared on common stock	(10,432)					(10,432)
Dividends on preferred stock	(3,161)					(3,161)
Stock-based compensation	5,286			5,286
Issuance of Series D preferred stock	121,151	125,000	0	(3,849)	0	0	0
Conversion of Series C preferred stock to common stock	0	(155)	4	151
Common stock issued for:
Acquisitions	19,171		422	18,749	0
Exercise of stock options and warrants	2,448		312	2,266	(130)
Restricted stock awards	160		93	352	(285)
Employee stock purchase plan	1,391		31	1,360
Director compensation plan	802		20	782
Balance at Jun. 30, 2015	$ 2,264,982	$ 251,312	$ 47,763	$ 1,159,052	$ (3,964)	$ 872,690	$ (61,871)