Consolidated Statements of Changes in Shareholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Series A Preferred Stock [Member]	Common Stock [Member]	Preferred Stock [Member]	Preferred Stock [Member] Series A Preferred Stock [Member]	Common Stock [Member]	Common Stock [Member] Common Stock [Member]	Surplus [Member]	Surplus [Member] Common Stock [Member]	Retained Earnings [Member]	Retained Earnings [Member] Series A Preferred Stock [Member]	Retained Earnings [Member] Common Stock [Member]	Accumulated Other Comprehensive Loss [Member]	Treasury Stock [Member]	Treasury Stock [Member] Common Stock [Member]
Beginning balance at Dec. 31, 2012	$ 1,502,377			$ 0		$ 69,494		$ 1,390,851		$ 93,495			$ (50,909)	$ (554)
Beginning balance, shares at Dec. 31, 2012						198,438
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	131,961									131,961
Total other comprehensive (loss) income	12,657												12,657
Cash dividends declared on common stock	(119,081)									(119,081)
Effect of stock incentive plan, net	5,472					$ 227		6,500		(34)				(1,221)
Effect of stock incentive plan, net, shares						380
Common stock dividend paid	0
Stock issued	7,654					$ 220		6,024		(1)				1,411
Stock issued, shares						775
Ending balance at Dec. 31, 2013	1,541,040			0		$ 69,941		1,403,375		106,340			(38,252)	(364)
Ending balance, shares at Dec. 31, 2013						199,593
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	116,172									116,172
Total other comprehensive (loss) income	(4,243)												(4,243)
Cash dividends declared on common stock	(91,581)									(91,581)
Effect of stock incentive plan, net	5,806					$ 234		6,269		(83)				(614)
Effect of stock incentive plan, net, shares						1,299
Stock issued	295,823					$ 10,897		284,108		(3)				821
Stock issued, shares						31,219
Ending balance at Dec. 31, 2014	1,863,017			0		$ 81,072		1,693,752		130,845			(42,495)	(157)
Ending balance, shares at Dec. 31, 2014						232,111
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	102,957									102,957
Total other comprehensive (loss) income	(3,200)												(3,200)
Cash dividends declared on common stock		$ (3,813)	$ (104,753)								$ (3,813)	$ (104,753)
Effect of stock incentive plan, net	4,715					$ 190		7,153		(30)				(2,598)
Effect of stock incentive plan, net, shares						500
Stock issued		$ 111,590	$ 236,578		$ 111,590		$ 7,364		$ 226,494			$ (35)			$ 2,755
Stock issued, shares		4,600					21,177
Ending balance at Dec. 31, 2015	$ 2,207,091			$ 111,590		$ 88,626		$ 1,927,399		$ 125,171			$ (45,695)	$ 0
Ending balance, shares at Dec. 31, 2015						253,788