Consolidated Statements Of Changes In Shareholders' Equity - USD ($) $ in Thousands	Total	Preferred stock	Common stock	Surplus	Treasury stock	Retained earnings	Accumulated other comprehensive income (loss)	Series C preferred stock	Series C preferred stock Preferred stock	Series C preferred stock Common stock	Series C preferred stock Surplus	Series C preferred stock Treasury stock	Series C preferred stock Retained earnings	Series C preferred stock Accumulated other comprehensive income (loss)	Series D preferred stock	Series D preferred stock Preferred stock	Series D preferred stock Common stock	Series D preferred stock Surplus	Series D preferred stock Treasury stock	Series D preferred stock Retained earnings
Balance at beginning of period 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	151,398	0	0	0	0	151,398	0
Other comprehensive income, net of tax	25,704	0	0	0	0	0	25,704
Cash dividends declared on common stock	(18,610)	0	0	0	0	(18,610)	0
Dividends on preferred stock	(6,323)	0	0	0	0	(6,323)	0
Stock-based compensation	7,754	0	0	7,754	0	0	0
Conversion of Series C Preferred Stock to common stock								$ 0	$ (10)	$ 1	$ 9	$ 0	$ 0	$ 0
Common stock issued for:
Exercise of stock options and warrants	4,639	0	538	4,414	(313)	0	0
Restricted stock awards	18	0	76	178	(236)	0	0
Employee stock purchase plan	3,004	0	65	2,939		0	0
Director compensation plan	1,649	0	20	1,629		0	0
Balance at end of period 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	156,749	0	0	0	0	156,749
Other comprehensive income, net of tax	(25,376)	0	0	0	0		(25,376)
Cash dividends declared on common stock	(21,069)	0	0	0	0	(21,069)
Dividends on preferred stock	(10,869)	0	0	0	0	(10,869)
Stock-based compensation	9,656	0	0	9,656	0	0
Issuance of stock															$ 120,842	$ 125,000	$ 0	$ (4,158)	$ 0	$ 0
Conversion of Series C Preferred Stock to common stock								0	(180)	4	176	0	0	0
Common stock issued for:
Acquisitions	38,723	0	811	37,912	0	0	0
Exercise of stock options and warrants	9,606	0	587	9,149	(130)	0	0
Restricted stock awards	(243)	0	108	(57)	(294)	0	0
Employee stock purchase plan	2,750	0	58	2,692	0	0	0
Director compensation plan	1,683	0	20	1,663		0	0
Balance at end of period 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	206,875	0	0	0	0	206,875	0
Other comprehensive income, net of tax	(2,620)	0	0	0	0	0	(2,620)
Cash dividends declared on common stock	(24,055)	0	0	0	0	(24,055)	0
Dividends on preferred stock	(14,513)	0	0	0	0	(14,513)	0
Stock-based compensation	9,303	0	0	9,303	0	0	0
Issuance of stock	152,911	0	3,000	149,911	0	0	0
Conversion of Series C Preferred Stock to common stock								$ 0	$ (30)	$ 1	$ 29	$ 0	$ 0	$ 0
Common stock issued for:
Exercise of stock options and warrants	11,228	0	329	11,276	(377)	0	0
Restricted stock awards	1	0	98	142	(239)	0	0
Employee stock purchase plan	2,637	0	56	2,581	0	0	0
Director compensation plan	1,576	0	25	1,551	0	0	0
Balance at end of period at Dec. 31, 2016	$ 2,695,617	$ 251,257	$ 51,978	$ 1,365,781	$ (4,589)	$ 1,096,518	$ (65,328)