CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDERS' EQUITY (unaudited) - USD ($) $ in Thousands	Total	Preferred Stock Series C Preferred Stock	Common Stock	Additional Paid-in Capital	Treasury Stock	Accumulated Other Comprehensive Income (Loss)	Retained Earnings
Balance at Dec. 31, 2015	$ 3,000,196	$ 125,980	$ 140,592	$ 2,989,981	$ (401,511)	$ (29,819)	$ 174,973
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	178,233						178,233
Other comprehensive income, net of income taxes	34,984					34,984
Cash dividends declared on common stock	(44,737)						(44,737)
Cash dividends paid on Series C Preferred Stock	(7,678)						(7,678)
Repurchases of common stock	(263,084)			(10,581)	(252,503)
Restricted share unit activity	(4,648)		301	(4,860)			(89)
Stock options exercised	2,981		173	2,808
Share-based compensation net tax benefit	199			199
Share-based compensation expense	10,213			10,213
Balance at Sep. 30, 2016	2,906,659	125,980	141,066	2,987,760	(654,014)	5,165	300,702
Balance at Jun. 30, 2016						11,005
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Other comprehensive income, net of income taxes	(5,840)					(5,840)
Balance at Sep. 30, 2016	2,906,659	125,980	141,066	2,987,760	(654,014)	5,165	300,702
Balance at Dec. 31, 2016	2,927,924	125,980	142,026	3,028,405	(664,595)	(55,659)	351,767
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	245,868						245,868
Other comprehensive income, net of income taxes	16,063					16,063
Cash dividends declared on common stock	(54,671)						(54,671)
Cash dividends paid on Series C Preferred Stock	(7,678)						(7,678)
Repurchases of common stock	(135,914)				(135,914)
Restricted share unit activity	(7,962)		335	(8,007)			(290)
Stock options exercised	2,872		164	2,708
Share-based compensation expense	10,576			10,576
Balance at Sep. 30, 2017	2,997,078	125,980	142,525	3,033,682	(800,509)	(39,596)	534,996
Balance at Jun. 30, 2017						(47,865)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Other comprehensive income, net of income taxes	8,269					8,269
Balance at Sep. 30, 2017	$ 2,997,078	$ 125,980	$ 142,525	$ 3,033,682	$ (800,509)	$ (39,596)	$ 534,996