CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY - USD ($) $ in Thousands	Total	Series A Preferred Stock	Series B Preferred Stock	Preferred Stock	Common Stock	Treasury Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Income (Loss)	Retained Earnings	Retained Earnings Series A Preferred Stock	Retained Earnings Series B Preferred Stock
Beginning Balance (in shares) at Dec. 31, 2014				7,300,000	423,438,848	(1,365,277)
Beginning Balance, shares issued (in shares) at Dec. 31, 2014					424,804,125
Beginning Balance at Dec. 31, 2014	$ 1,829,958			$ 565,000	$ 84,961	$ (12,187)	$ 1,090,511	$ (11,393)	$ 113,066
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	184,439								184,439
Other comprehensive loss, net of tax	(12,122)							(12,122)
Total comprehensive income	172,317
Cash dividends:
Cash dividends, preferred stock		$ (8,625)	$ (5,981)							$ (8,625)	$ (5,981)
Dividend equivalent units related to employee stock-based compensation plans	$ 0						1,138		(1,138)
Issuance of common shares (in shares)	5,569,853				5,569,853
Issuance of common shares	$ 15,443				$ 1,114		14,329
Tax benefit related to employee stock-based compensation	6,093						6,093
Stock-based compensation expense	16,423						16,423
Shares repurchased related to employee stock-based compensation plans (in shares)					(2,900,266)	(2,900,266)
Shares repurchased related to employee stock-based compensation plans	(28,294)					$ (28,294)
Ending Balance (in shares) at Sep. 30, 2015				7,300,000	426,108,435	(4,265,543)
Ending Balance, shares issued (in shares) at Sep. 30, 2015					430,373,978
Ending Balance at Sep. 30, 2015	1,997,334			$ 565,000	$ 86,075	$ (40,481)	1,128,494	(23,515)	281,761
Beginning Balance (in shares) at Dec. 31, 2015				7,300,000	426,303,244	(4,374,190)
Beginning Balance, shares issued (in shares) at Dec. 31, 2015					430,677,434
Beginning Balance at Dec. 31, 2015	2,096,323			$ 565,000	$ 86,136	$ (41,223)	1,135,860	(16,059)	366,609
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	180,085								180,085
Other comprehensive loss, net of tax	(11,754)							(11,754)
Total comprehensive income	168,331
Cash dividends:
Cash dividends, preferred stock		$ (8,625)	$ (7,073)							$ (8,625)	$ (7,073)
Dividend equivalent units related to employee stock-based compensation plans	$ 0						402		(402)
Issuance of common shares (in shares)	3,727,574				3,727,574
Issuance of common shares	$ 6,238				$ 745		5,493
Tax deficiency related to employee stock-based compensation	(2,457)						(2,457)
Stock-based compensation expense	17,950						17,950
Shares repurchased related to employee stock-based compensation plans (in shares)					(1,763,092)	(1,763,092)
Shares repurchased related to employee stock-based compensation plans	(11,191)					$ (11,191)
Ending Balance (in shares) at Sep. 30, 2016				7,300,000	428,267,726.000	(6,137,282.000)
Ending Balance, shares issued (in shares) at Sep. 30, 2016					434,405,008.000
Ending Balance at Sep. 30, 2016	$ 2,259,496			$ 565,000	$ 86,881	$ (52,414)	$ 1,157,248	$ (27,813)	$ 530,594