Consolidated Statements of Changes in Shareholders' Equity (USD $) In Thousands, unless otherwise specified	Total	Preferred Stock	Common Stock	Warrant	Capital Surplus	Accumulated Other Comprehensive Income (Loss)	Retained Earnings	Treasury Stock
Beginning Balance at Dec. 31, 2013	$ 2,702,894	$ 100,000	$ 127,937	$ 3,000	$ 1,390,643	$ (66,876)	$ 1,277,975	$ (129,785)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	53,455						53,455
Total other comprehensive gains/(losses), Net of Tax	11,372					11,372
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	64,827					11,372	53,455
Dividends, Preferred Stock, Cash	(1,469)						(1,469)
Cash dividends - common stock	(26,335)						(26,335)
Nonvested (restricted) shares granted	0				(1,485)			1,485
Restricted Stock Activity	(717)				419			(1,136)
Deferred compensation trust	0				406			(406)
Share-based compensation	3,766				3,766
Ending Balance at Mar. 31, 2014	2,742,966	100,000	127,937	3,000	1,393,749	(55,504)	1,303,626	(129,842)
Beginning Balance at Dec. 31, 2014	2,834,281	100,000	127,937	3,000	1,393,090	(71,892)	1,404,717	(122,571)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	57,139	0	0	0	0	0	57,139	0
Total other comprehensive gains/(losses), Net of Tax	22,625					22,625
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent						22,625	57,139
Dividends, Preferred Stock, Cash	(1,469)	0	0	0	0	0	(1,469)	0
Cash dividends - common stock	(26,461)			0		0	(26,461)	0
Nonvested (restricted) shares granted	0			0	(2,631)	0	0	2,631
Restricted Stock Activity	970			0	(326)	0	0	1,296
Deferred compensation trust	0			0	(507)	0	0	507
Share-based compensation	(3,641)			0	(3,641)	0	0	0
Ending Balance at Mar. 31, 2015	$ 2,888,786	$ 100,000	$ 127,937	$ 3,000	$ 1,394,933	$ (49,267)	$ 1,433,926	$ (121,743)