Consolidated Statements of Shareholders' Equity - USD ($) $ in Thousands	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, at cost [Member]	Accumulated Other Comprehensive Loss, Net of Tax [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	179,456						179,456
Other comprehensive loss, net of tax	(16,283)										(16,283)
Dividends and dividend equivalents declared on common stock	(49,145)					19	(49,164)
Dividends on preferred stock $85.00, $85.00, and $21.25 per share on Series A for 2013, 2014, and 2015, respectively and $1,648.89, $1,600.00, and $1,600.00 per share on Series E for 2013, 2014 and 2015, respectively		$ (2,460)	$ (8,343)					$ (2,460)	$ (8,343)
Common stock issued	731				27	(20,737)	(36,256)			57,697
Stock-based compensation, net of tax impact	9,575					2,813	(3,265)			10,027
Exercise of stock options	2,736					(2,101)				4,837
Shares acquired related to employee share-based compensation plans	(672)									(672)
Common stock warrants repurchased	(30)					(30)
Ending Balance at Dec. 31, 2013	2,209,348			151,649	934	1,125,584	1,080,648			(100,918)	(48,549)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of change in accounting principal	253						253
Net income	199,726						199,726
Other comprehensive loss, net of tax	(7,712)										(7,712)
Dividends and dividend equivalents declared on common stock	(67,690)					57	(67,747)
Dividends on preferred stock $85.00, $85.00, and $21.25 per share on Series A for 2013, 2014, and 2015, respectively and $1,648.89, $1,600.00, and $1,600.00 per share on Series E for 2013, 2014 and 2015, respectively		(2,460)	(8,096)					(2,460)	(8,096)
Common stock issued	435				2	433
Stock-based compensation, net of tax impact	10,113					3,223	180			6,710
Exercise of stock options	2,221					(1,760)				3,981
Shares acquired related to employee share-based compensation plans	(2,326)									(2,326)
Common stock repurchased	(10,741)									(10,741)
Common stock warrants repurchased	(3)					(3)
Ending Balance at Dec. 31, 2014	2,322,815			151,649	936	1,127,534	1,202,251			(103,294)	(56,261)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	206,340						206,340
Other comprehensive loss, net of tax	(21,845)										(21,845)
Dividends and dividend equivalents declared on common stock	(81,197)					119	(81,316)
Dividends on preferred stock $85.00, $85.00, and $21.25 per share on Series A for 2013, 2014, and 2015, respectively and $1,648.89, $1,600.00, and $1,600.00 per share on Series E for 2013, 2014 and 2015, respectively		$ (615)	$ (8,096)					$ (615)	$ (8,096)
Common stock issued	0				1	(1)
Preferred stock conversion	0			(28,939)		(3,429)				32,368
Stock-based compensation, net of tax impact	12,947					2,906	(1,005)			11,046
Exercise of stock options	3,060					(2,781)				5,841
Shares acquired related to employee share-based compensation plans	(5,251)									(5,251)
Common stock repurchased	(12,564)									(12,564)
Common stock warrants repurchased	(23)					(23)
Ending Balance at Dec. 31, 2015	$ 2,415,571			$ 122,710	$ 937	$ 1,124,325	$ 1,317,559			$ (71,854)	$ (78,106)