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	113,265					113,265
Other comprehensive income (loss), net of tax	20,336						20,336
Cash dividends declared on common stock	(13,938)					(13,938)
Dividends on preferred stock	(4,743)					(4,743)
Stock-based compensation	5,754			5,754	0
Conversion of Series C preferred stock to common stock	0	(10)	1	9
Common stock issued for:
Exercise of stock options and warrants	3,934		450	3,797	(313)
Restricted stock awards	12		67	151	(206)
Employee stock purchase plan	2,133		47	2,086
Director compensation plan	1,166		20	1,146
Balance at Sep. 30, 2014	2,028,508	126,467	46,766	1,129,975	(3,519)	771,519	(42,700)
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	121,238					121,238	0
Other comprehensive income (loss), net of tax	(11,761)						(11,761)
Cash dividends declared on common stock	(15,746)					(15,746)
Dividends on preferred stock	(7,240)					(7,240)
Stock-based compensation	7,817			7,817
Issuance of Series D preferred stock	120,842	125,000	0	(4,158)	0	0	0
Conversion of Series C preferred stock to common stock	0	(155)	4	151
Common stock issued for:
Acquisitions	38,723		811	37,912	0
Exercise of stock options and warrants	8,575		564	8,141	(130)
Restricted stock awards	196		99	382	(285)
Employee stock purchase plan	2,040		43	1,997
Director compensation plan	1,230		20	1,210
Balance at Sep. 30, 2015	$ 2,335,736	$ 251,312	$ 48,422	$ 1,187,407	$ (3,964)	$ 901,652	$ (49,093)