Consolidated Statements Of Changes In Shareholders' Equity (USD $) In Thousands	Common Stock [Member]	Preferred Stock [Member]	Surplus [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Loss [Member]	Treasury Stock [Member]	Total
Balance at Dec. 31, 2007
Cumulative effect of adoption of a new accounting principle (ASC Topic 320)				$ 8,605	$ (8,605)
Balance (Before Adjustment [Member])	48,228	291,539	1,047,085	85,234	(60,931)	(47,546)	1,363,609
Balance at Dec. 31, 2008	48,228	291,539	1,047,085	93,839	(69,536)	(47,546)	1,363,609
Balance, shares (Before Adjustment [Member])	156,307
Balance, shares at Dec. 31, 2008	156,307
Net income				116,061			116,061
Other comprehensive income (loss), net of tax					49,720		49,720
Preferred stock redemption		(300,000)					(300,000)
Accretion of discount on preferred stock		8,461		(8,461)
Cash dividends declared on preferred stock				(11,063)			(11,063)
Cash dividends declared on common stock				(110,101)			(110,101)
Effect of stock incentive plan, net	(32)		1,725	(2,121)		4,319	3,891
Effect of stock incentive plan, net, shares	191
Common stock dividend declared			(101,051)				(101,051)
Common stock dividend paid	2,363		98,650				101,013
Common stock issued	3,734		131,562	(4,562)		9,020	139,754
Common stock issued, shares	12,171
Fair value of stock options granted			1,021				1,021
Balance at Dec. 31, 2009	54,293		1,178,992	73,592	(19,816)	(34,207)	1,252,854
Balance, shares at Dec. 31, 2009	168,669
Cumulative effect of adoption of a new accounting principle (ASC Topic 320)					14,097
Net income				131,170			131,170
Other comprehensive income (loss), net of tax					14,097		14,097
Cash dividends declared on common stock				(116,137)			(116,137)
Effect of stock incentive plan, net	65		1,322	(2,603)		5,313	4,097
Effect of stock incentive plan, net, shares	216
Common stock dividend declared			(110,848)				(110,848)
Common stock dividend paid	2,683		108,015				110,698
Common stock issued	649			(6,219)		14,649	8,430
Fair value of stock options granted			844				844
Balance at Dec. 31, 2010	57,041		1,178,325	79,803	(5,719)	(14,245)	1,295,205
Balance, shares at Dec. 31, 2010	169,534
Net income				133,653			133,653
Other comprehensive income (loss), net of tax					(56,722)		(56,722)
Cash dividends declared on common stock				(117,071)			(117,071)
Effect of stock incentive plan, net	61		3,095	(396)		210	2,970
Effect of stock incentive plan, net, shares	(39)
Common stock dividend declared			(109,675)				(109,675)
Common stock dividend paid	2,831		106,844				109,675
Common stock issued	22		546	(5,978)		13,623	8,213
Common stock issued, shares	679
Balance at Dec. 31, 2011	$ 59,955		$ 1,179,135	$ 90,011	$ (62,441)	$ (412)	$ 1,266,248
Balance, shares at Dec. 31, 2011	170,174