Condensed Consolidated Statements of Shareholders' Equity (Unaudited) (USD $) In Thousands, unless otherwise specified	Total	Series A Preferred Stock [Member]	Series E Preferred Stock [Member]	Preferred Stock [Member]	Common Stock [Member]	Paid-In Capital [Member]	Retained Earnings [Member]	Retained Earnings [Member] Series A Preferred Stock [Member]	Retained Earnings [Member] Series E Preferred Stock [Member]	Treasury Stock [Member]	Accumulated Other Comprehensive Loss [Member]
Beginning Balance at Dec. 31, 2012	$ 2,093,530			$ 151,649	$ 907	$ 1,145,620	$ 1,000,427			$ (172,807)	$ (32,266)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	135,795						135,795
Other comprehensive income (loss), net of tax	(26,675)										(26,675)
Dividends paid on common stock of $0.55 and $0.40 per share during 9 months ended September 30, 2014 and 2013, respectively	(35,270)					10	(35,280)
Dividends paid on preferred stock $63.75 per share on Series A for both 9 months ended September 30, 2014 and 2013 and $1,200.00 and $1,248.89 per share on Series E for 9 months ended September 30, 2014 and 2013, respectively	(8,164)	(1,845)	(6,319)					(1,845)	(6,319)
Common stock warrants repurchased	(30)					(30)
Exercise of stock options	984					(729)				1,713
Shares acquired related to employee share-based compensation plans	(381)									(381)
Stock-based compensation, net of tax impact	7,675					2,747	(2,407)			7,335
Common stock issued	195				26	(21,274)	(36,254)			57,697
Ending Balance at Sep. 30, 2013	2,167,659			151,649	933	1,126,344	1,054,117			(106,443)	(58,941)
Beginning Balance at Dec. 31, 2013	2,209,188			151,649	934	1,125,584	1,080,488			(100,918)	(48,549)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	148,737						148,737
Other comprehensive income (loss), net of tax	12,630										12,630
Dividends paid on common stock of $0.55 and $0.40 per share during 9 months ended September 30, 2014 and 2013, respectively	(49,631)					41	(49,672)
Dividends paid on preferred stock $63.75 per share on Series A for both 9 months ended September 30, 2014 and 2013 and $1,200.00 and $1,248.89 per share on Series E for 9 months ended September 30, 2014 and 2013, respectively	(7,917)	(1,845)	(6,072)					(1,845)	(6,072)
Exercise of stock options	1,739					(1,517)				3,256
Common stock repurchased	(10,741)									(10,741)
Shares acquired related to employee share-based compensation plans	(2,218)									(2,218)
Stock-based compensation, net of tax impact	8,627					3,909	736			3,982
Common stock issued	436					436
Ending Balance at Sep. 30, 2014	$ 2,310,850			$ 151,649	$ 934	$ 1,128,453	$ 1,172,372			$ (106,639)	$ (35,919)