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, 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
Other comprehensive income, 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 stock	121,151	125,000		(3,849)
Conversion of Series C preferred stock to common stock	0	(155)	4	151
Common stock issued for:
Acquisitions	19,171		422	18,749
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)
Balance at Dec. 31, 2015	2,352,274	251,287	48,469	1,190,988	(3,973)	928,211	(62,708)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	99,152					99,152	0
Other comprehensive income, net of tax	28,268						28,268
Cash dividends declared on common stock	(11,643)					(11,643)
Dividends on preferred stock	(7,256)					(7,256)
Stock-based compensation	4,752			4,752
Issuance of stock	152,823		3,000	149,823
Conversion of Series C preferred stock to common stock	0	(30)	1	29
Common stock issued for:
Exercise of stock options and warrants	3,088		97	2,991
Restricted stock awards	29		87	114	(172)
Employee stock purchase plan	1,299		29	1,270
Director compensation plan	809		25	784
Balance at Jun. 30, 2016	$ 2,623,595	$ 251,257	$ 51,708	$ 1,350,751	$ (4,145)	$ 1,008,464	$ (34,440)