Consolidated Statements Of Changes In Shareholders' Equity (USD $) In Thousands, unless otherwise specified	Total	Preferred Stock [Member]	Common Stock [Member]	Surplus [Member]	Treasury Stock [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Series B Preferred Stock [Member]	Series C Preferred Stock [Member]
Balance at Dec. 31, 2009	$ 1,138,639	$ 284,824	$ 27,079	$ 589,939	$ (122,733)	$ 366,152	$ (6,622)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	63,329	0	0	0	0	63,329	0
Other comprehensive income, net of tax	1,266	0	0	0	0	0	1,266
Cash dividends declared on common stock	(4,991)	0	0	0	0	(4,991)	0
Dividends on preferred stock	(16,188)	0	0	0	0	(16,188)	0
Accretion on preferred stock	0	3,455	0	0	0	(3,455)	0
Redemption of Series B preferred stock		(250,000)	0	0	0	0	0	(250,000)
Non-cash deemed preferred stock dividend	0	11,361	0	0	0	(11,361)	0
Stock-based compensation	4,640	0	0	4,640	0	0	0
Cumulative Effect of Prospective Application of New Accounting Principle	(1,288)	0	0	0	0	(1,132)	(156)
Issuance of prepaid common stock purchase contracts	179,316	0	0	179,316	0	0	0
Common stock issued for:
New issuance, net of costs	315,108	0	7,473	184,684	122,951	0	0
Exercise of stock options and warrants	3,295	0	159	3,136	0	0	0
Restricted stock awards	(241)	0	64	(87)	(218)	0	0
Employee stock purchase plan	1,395	0	41	1,354	0	0	0
Director compensation plan	2,269	0	48	2,221	0	0	0
Balance at Dec. 31, 2010	1,436,549	49,640	34,864	965,203	0	392,354	(5,512)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	77,575	0	0	0	0	77,575	0
Other comprehensive income, net of tax	2,634	0	0	0	0	0	2,634
Cash dividends declared on common stock	(6,344)	0	0	0	0	(6,344)	0
Dividends on preferred stock	(4,000)	0	0	0	0	(4,000)	0
Accretion on preferred stock	0	128	0	0	0	(128)	0
Common stock repurchases	(112)	0	0	0	(112)	0	0
Stock-based compensation	5,692	0	0	5,692	0	0	0
Common stock issued for:
Acquisitions	26,486	0	883	25,603	0	0	0
Exercise of stock options and warrants	1,590	0	86	1,504	0	0	0
Restricted stock awards	(75)	0	57	(132)	0	0	0
Employee stock purchase plan	2,099	0	67	2,032	0	0	0
Director compensation plan	1,439	0	25	1,414	0	0	0
Balance at Dec. 31, 2011	1,543,533	49,768	35,982	1,001,316	(112)	459,457	(2,878)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	111,196	0	0	0	0	111,196	0
Other comprehensive income, net of tax	10,589	0	0	0	0	0	10,589
Cash dividends declared on common stock	(6,537)	0	0	0	0	(6,537)	0
Dividends on preferred stock	(8,955)	0	0	0	0	(8,955)	0
Accretion on preferred stock	0	138	0	0	0	(138)	0
Stock-based compensation	9,072	0	0	9,072	0	0	0
Common stock issued for:
New issuance, net of costs		126,500	0	(3,810)	0	0	0		122,690
Acquisitions	14,560	0	398	14,162	0	0	0
Exercise of stock options and warrants	5,690	0	503	11,904	(6,717)	0	0
Restricted stock awards	(994)	0	132	(117)	(1,009)	0	0
Employee stock purchase plan	2,325	0	71	2,254	0	0	0
Director compensation plan	1,536	0	22	1,514	0	0	0
Balance at Dec. 31, 2012	$ 1,804,705	$ 176,406	$ 37,108	$ 1,036,295	$ (7,838)	$ 555,023	$ 7,711