CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY - USD ($) $ in Thousands	Total	Series B Preferred Stock	Preferred Stock	Common Stock	Treasury Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Income (Loss)	Retained Earnings	Retained Earnings Series B Preferred Stock
Beginning Balance (in shares) at Dec. 31, 2017			4,000,000	432,376,250	(11,087,337)
Beginning Balance, issued (in shares) at Dec. 31, 2017				443,463,587
Beginning Balance at Dec. 31, 2017	$ 2,474,256		$ 400,000	$ 88,693	$ (107,644)	$ 1,222,277	$ 2,748	$ 868,182
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	339,964							339,964
Other comprehensive income, net of tax	23,402						23,402
Total comprehensive income	$ 363,366
Reclassification resulting from the adoption of ASU No. 2018-02							592	(592)
Cash dividends:
Preferred Stock		$ (11,441)							$ (11,441)
Issuance of common shares (in shares)	6,341,950			6,341,950
Issuance of common shares	$ 21,927			$ 1,269		20,658
Stock-based compensation expense	$ 25,828					25,828
Common stock repurchased (in shares)	0
Shares repurchased related to employee stock-based compensation plans (in shares)	(3,056,746)			(3,056,746)	3,056,746
Shares repurchased related to employee stock-based compensation plans	$ (34,653)				$ (34,653)
Ending Balance (in shares) at Sep. 30, 2018			4,000,000	435,661,454	(14,144,083)
Ending Balance, issued (in shares) at Sep. 30, 2018				449,805,537
Ending Balance at Sep. 30, 2018	2,840,335		$ 400,000	$ 89,962	$ (142,297)	1,268,763	27,012	1,196,895
Beginning Balance (in shares) at Jun. 30, 2018			4,000,000	435,380,601	(14,027,932)
Beginning Balance, issued (in shares) at Jun. 30, 2018				449,408,533
Beginning Balance at Jun. 30, 2018	2,728,702		$ 400,000	$ 89,882	$ (140,956)	1,260,201	23,216	1,096,359
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	103,878							103,878
Other comprehensive income, net of tax	3,526						3,526
Total comprehensive income	107,404
Reclassification resulting from the adoption of ASU No. 2018-02	$ 1,052						270	782
Cash dividends:
Preferred Stock		(4,124)							(4,124)
Issuance of common shares (in shares)	397,004			397,004
Issuance of common shares	$ 3,075			$ 80		2,995
Stock-based compensation expense	$ 5,567					5,567
Common stock repurchased (in shares)	0
Shares repurchased related to employee stock-based compensation plans (in shares)	(116,151)			(116,151)	116,151
Shares repurchased related to employee stock-based compensation plans	$ (1,341)				$ (1,341)
Ending Balance (in shares) at Sep. 30, 2018			4,000,000	435,661,454	(14,144,083)
Ending Balance, issued (in shares) at Sep. 30, 2018				449,805,537
Ending Balance at Sep. 30, 2018	2,840,335		$ 400,000	$ 89,962	$ (142,297)	1,268,763	27,012	1,196,895
Beginning Balance (in shares) at Dec. 31, 2018			4,000,000	435,681,488	(14,174,733)
Beginning Balance, issued (in shares) at Dec. 31, 2018				449,856,221
Beginning Balance at Dec. 31, 2018	2,972,656		$ 400,000	$ 89,972	$ (142,591)	1,274,635	10,623	1,340,017
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	436,924							436,924
Other comprehensive income, net of tax	(30,806)						(30,806)
Total comprehensive income	406,118
Cash dividends:
Common Stock	$ (38,485)							(38,485)
Preferred Stock		(12,952)							(12,952)
Dividend equivalent units related to employee stock-based compensation plans						5		(5)
Issuance of common shares (in shares)	3,677,821			3,677,821
Issuance of common shares	$ 3,119			$ 735		2,384
Stock-based compensation expense	$ 24,779					24,604		175
Common stock repurchased (in shares)	(15,861,718)			(15,861,718)	15,861,718
Common stock repurchased	$ (157,597)				$ (157,597)
Shares repurchased related to employee stock-based compensation plans (in shares)	(1,328,665)			(1,328,665)	1,328,665
Shares repurchased related to employee stock-based compensation plans	$ (14,506)				$ (14,506)
Ending Balance (in shares) at Sep. 30, 2019			4,000,000	422,168,926	(31,365,116)
Ending Balance, issued (in shares) at Sep. 30, 2019				453,534,042
Ending Balance at Sep. 30, 2019	3,183,132		$ 400,000	$ 90,707	$ (314,694)	1,301,628	(20,183)	1,725,674
Beginning Balance (in shares) at Jun. 30, 2019			4,000,000	426,594,990	(26,912,915)
Beginning Balance, issued (in shares) at Jun. 30, 2019				453,507,905
Beginning Balance at Jun. 30, 2019	3,097,316		$ 400,000	$ 90,702	$ (277,071)	1,296,409	(13,579)	1,600,855
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	128,458							128,458
Other comprehensive income, net of tax	(6,604)						(6,604)
Total comprehensive income	121,854
Cash dividends:
Preferred Stock		$ (4,153)							$ (4,153)
Common stock dividend accrual adjustment	$ 339							339
Issuance of common shares (in shares)	26,137			26,137
Issuance of common shares	$ 92			$ 5		87
Stock-based compensation expense	$ 5,307					5,132		175
Common stock repurchased (in shares)	(4,436,963)			(4,436,963)	4,436,963
Common stock repurchased	$ (37,477)				$ (37,477)
Shares repurchased related to employee stock-based compensation plans (in shares)	(15,238)			(15,238)	15,238
Shares repurchased related to employee stock-based compensation plans	$ (146)				$ (146)
Ending Balance (in shares) at Sep. 30, 2019			4,000,000	422,168,926	(31,365,116)
Ending Balance, issued (in shares) at Sep. 30, 2019				453,534,042
Ending Balance at Sep. 30, 2019	$ 3,183,132		$ 400,000	$ 90,707	$ (314,694)	$ 1,301,628	$ (20,183)	$ 1,725,674