Consolidated Statements Of Shareholders' Equity (USD $) In Thousands, unless otherwise specified	Preferred Stock [Member]	Common Stock [Member]	Additional Paid-In Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income [Member]	Treasury Stock [Member]	Total
Balance at Dec. 31, 2008	$ 87,779	$ 17,677	$ 474,209	$ 218,818	$ 12,294	$ (76,569)	$ 734,208
Comprehensive income:
Net income				158,354			158,354
Change in unrealized gain on securities available for sale, net of deferred taxes					(2,592)		(2,592)
Change in fair value of derivatives used for cash flow hedges, net of tax effect					12,714		12,714
Total comprehensive income							168,476
Cash dividends declared, $1.36 per share				(25,003)			(25,003)
Preferred stock dividend and accretion	99			(3,350)			(3,251)
Preferred stock redemption	(87,878)						(87,878)
Redemption of preferred stock warrant			(1,200)				(1,200)
Reissuance of treasury stock under incentive plan, net of shares surrendered in payment, including tax benefit			(497)			5,328	4,831
Common Stock Issued for acquisitions		4,430	160,214				164,644
Common stock issued for recognition and retention plan			(7,226)			7,226
Share-based compensation cost			6,586				6,586
Equity contribution to joint venture				(95)			(95)
Balance at Dec. 31, 2009		22,107	632,086	348,724	22,416	(64,015)	961,318
Comprehensive income:
Net income				48,826			48,826
Change in unrealized gain on securities available for sale, net of deferred taxes					(5,066)		(5,066)
Change in fair value of derivatives used for cash flow hedges, net of tax effect					(2,670)		(2,670)
Total comprehensive income							41,090
Cash dividends declared, $1.36 per share				(36,495)			(36,495)
Reissuance of treasury stock under incentive plan, net of shares surrendered in payment, including tax benefit			(611)			1,378	767
Common Stock Issued for acquisitions		5,973	323,007				328,980
Common stock issued for recognition and retention plan			(5,415)			5,415
Share-based compensation cost			7,797				7,797
Balance at Dec. 31, 2010		28,080	956,864	361,055	14,680	(57,222)	1,303,457
Comprehensive income:
Net income				53,538			53,538
Change in unrealized gain on securities available for sale, net of deferred taxes					21,058		21,058
Change in fair value of derivatives used for cash flow hedges, net of tax effect					(11,281)		(11,281)
Total comprehensive income							63,315
Cash dividends declared, $1.36 per share				(39,409)			(39,409)
Reissuance of treasury stock under incentive plan, net of shares surrendered in payment, including tax benefit			(2,596)			9,026	6,430
Common Stock Issued for acquisitions		3,083	178,057				181,140
Common stock issued for recognition and retention plan			(5,559)			5,559
Treasury stock acquired at cost, 900,000 shares						(41,386)	(41,386)
Share-based compensation cost			9,114				9,114
Balance at Dec. 31, 2011		$ 31,163	$ 1,135,880	$ 375,184	$ 24,457	$ (84,023)	$ 1,482,661