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, 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
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
Conversion of Series C preferred stock to common stock	0	(30)	1	29
Common stock issued for:
New issuance, net of costs	152,823		3,000	149,823
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)
Balance at Dec. 31, 2016	2,695,617	251,257	51,978	1,365,781	(4,589)	1,096,518	(65,328)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	123,275					123,275
Other comprehensive income, net of tax	18,791						18,791
Cash dividends declared on common stock	(15,118)					(15,118)
Dividends on preferred stock	(5,678)					(5,678)
Stock-based compensation	5,746			5,746
Conversion of Series C preferred stock to common stock	0	(126,257)	3,121	123,136
Common stock issued for:
Exercise of stock options and warrants	15,061		573	14,488	0
Restricted stock awards	(295)		79	(79)	(295)
Employee stock purchase plan	1,249		19	1,230
Director compensation plan	810		32	778
Balance at Jun. 30, 2017	$ 2,839,458	$ 125,000	$ 55,802	$ 1,511,080	$ (4,884)	$ 1,198,997	$ (46,537)