Consolidated Statements of Changes in Stockholders' Equity (Unaudited) - USD ($) $ in Thousands	Total	Cumulative Effect, Period Of Adoption, Adjustment	Cumulative Effect, Period Of Adoption, Adjusted Balance	Performance/Service Based RSAs, RSA,	Board Authorized Purchase Program [Member]	Series C Preferred Stock	Series D Preferred Stock	Series E Preferred Stock	Series F Preferred Stock	Preferred Equity	Preferred Equity Cumulative Effect, Period Of Adoption, Adjusted Balance	Common Stock	Common Stock Cumulative Effect, Period Of Adoption, Adjusted Balance	Surplus	Surplus Cumulative Effect, Period Of Adoption, Adjusted Balance	Retained Earnings	Retained Earnings Cumulative Effect, Period Of Adoption, Adjustment	Retained Earnings Cumulative Effect, Period Of Adoption, Adjusted Balance	Accumulated Other Comprehensive Income (Loss)	Accumulated Other Comprehensive Income (Loss) Cumulative Effect, Period Of Adoption, Adjusted Balance	Treasury Stock	Treasury Stock Cumulative Effect, Period Of Adoption, Adjusted Balance	Treasury Stock Performance/Service Based RSAs, RSA,	Treasury Stock Board Authorized Purchase Program [Member]
Beginning balance at Dec. 31, 2018	$ 3,780,888									$ 256,716		$ 1,752		$ 1,712,615		$ 2,181,414			$ (124,972)		$ (246,638)
Comprehensive income
Net income	86,686															86,686
Other comprehensive income (loss)	21,597																		21,597
Comprehensive income	108,283
Common stock issued
Shares Issued, Value, Share-based Payment Arrangement, after Forfeiture	7,045													(32,220)		0					39,265
Purchase of treasury stock,				$ (7,468)	$ (29,999)																		$ (7,468)	$ (29,999)
Cash dividends
Common stock ($0.17 per share in 2019 and $0.18 per share in 2020)	(28,183)															(28,183)
Preferred stock(a)	(3,801)															(3,801)
Stock-based compensation expense, net	9,397													9,397
Stockholders' Equity, Other	(293)															(293)
Ending balance at Mar. 31, 2019	3,835,870									256,716		1,752		1,689,792		2,235,824			(103,375)		(244,840)
Cash dividends
Preferred Stock, Dividends, Per Share, Cash Paid						$ 0.3828125	$ 0.3359375	$ 0.3671875
Beginning balance at Dec. 31, 2018	3,780,888									256,716		1,752		1,712,615		2,181,414			(124,972)		(246,638)
Comprehensive income
Net income	254,686
Other comprehensive income (loss)	88,020																		88,020
Comprehensive income	342,706
Ending balance at Sep. 30, 2019	3,920,855									256,716		1,752		1,713,971		2,341,158			(36,953)		(355,791)
Beginning balance at Mar. 31, 2019	3,835,870									256,716		1,752		1,689,792		2,235,824			(103,375)		(244,840)
Comprehensive income
Net income	84,661															84,661
Other comprehensive income (loss)	44,311																		44,311
Comprehensive income	128,972
Common stock issued
Shares Issued, Value, Share-based Payment Arrangement, after Forfeiture	827													(211)		0					1,038
Purchase of treasury stock,				(831)	(39,602)																		(831)	(39,602)
Cash dividends
Common stock ($0.17 per share in 2019 and $0.18 per share in 2020)	(27,776)															(27,776)
Preferred stock(a)	(3,801)															(3,801)
Stock-based compensation expense, net	6,134													6,134
Ending balance at Jun. 30, 2019	3,899,794									256,716		1,752		1,695,715		2,288,909			(59,063)		(284,235)
Cash dividends
Preferred Stock, Dividends, Per Share, Cash Paid						0.3828125	0.3359375	0.3671875
Net income	83,339															83,339
Other comprehensive income (loss)	22,111																		22,111
Comprehensive income	105,450
Shares Issued, Value, Share-based Payment Arrangement, after Forfeiture	1,198													12,561		0					(11,363)
Purchase of treasury stock,				(194)	(59,999)																		(194)	(59,999)
Common stock ($0.17 per share in 2019 and $0.18 per share in 2020)	(27,289)															(27,289)
Preferred stock(a)	(3,801)															(3,801)
Stock-based compensation expense, net	5,696													5,696
Ending balance at Sep. 30, 2019	3,920,855									256,716		1,752		1,713,971		2,341,158			(36,953)		(355,791)
Cash dividends
Preferred Stock, Dividends, Per Share, Cash Paid						0.3828125	0.3359375	0.3671875
Beginning balance at Dec. 31, 2019	3,922,124		$ 3,823,787							256,716	$ 256,716	1,752	$ 1,752	1,716,431	$ 1,716,431	2,380,867		$ 2,282,530	(33,183)	$ (33,183)	(400,460)	$ (400,460)
Beginning balance (Accounting Standards Update 2016-13) at Dec. 31, 2019		$ (98,337)															$ (98,337)
Comprehensive income
Net income	45,838															45,838
Other comprehensive income (loss)	16,209																		16,209
Comprehensive income	62,046
Common stock issued
Shares Issued, Value, Share-based Payment Arrangement, after Forfeiture	2,896													(20,659)							23,555
Purchase of treasury stock,				(5,555)	$ (71,255)																		(5,555)	$ (71,255)
Cash dividends
Common stock ($0.17 per share in 2019 and $0.18 per share in 2020)	(28,392)															(28,392)
Preferred stock(a)	(3,801)															(3,801)
Stock-based compensation expense, net	10,744													10,744
Ending balance at Mar. 31, 2020	3,790,471									256,716		1,752		1,706,516		2,296,176			(16,974)		(453,714)
Cash dividends
Preferred Stock, Dividends, Per Share, Cash Paid						0.3828125	0.3359375	0.3671875
Beginning balance at Dec. 31, 2019	3,922,124		$ 3,823,787							256,716	$ 256,716	1,752	$ 1,752	1,716,431	$ 1,716,431	2,380,867		$ 2,282,530	(33,183)	$ (33,183)	(400,460)	$ (400,460)
Beginning balance (Accounting Standards Update 2016-13) at Dec. 31, 2019		$ (98,337)															$ (98,337)
Comprehensive income
Net income	239,769															239,769
Other comprehensive income (loss)	37,178																		37,178
Comprehensive income	276,948
Ending balance at Sep. 30, 2020	4,045,433									353,637		1,752		1,717,186		2,424,992			3,995		(456,129)
Beginning balance at Mar. 31, 2020	3,790,471									256,716		1,752		1,706,516		2,296,176			(16,974)		(453,714)
Comprehensive income
Net income	148,718															148,718
Other comprehensive income (loss)	15,054																		15,054
Comprehensive income	163,772
Common stock issued
Shares Issued, Value, Share-based Payment Arrangement, after Forfeiture	173													1,523							(1,350)
Purchase of treasury stock,				7																			7
Cash dividends
Common stock ($0.17 per share in 2019 and $0.18 per share in 2020)	(27,889)															(27,889)
Preferred stock(a)	(4,144)															(4,144)
Issuance of preferred stock	97,129									97,129
Stock-based compensation expense, net	4,939													4,939
Ending balance at Jun. 30, 2020	4,024,457									353,846		1,752		1,712,978		2,412,859			(1,920)		(455,057)
Cash dividends
Preferred Stock, Dividends, Per Share, Cash Paid						0.3828125	0.3359375	0.3671875	$ 0.0849931
Net income	45,214															45,214
Other comprehensive income (loss)	5,916																		5,916
Comprehensive income	51,130
Shares Issued, Value, Share-based Payment Arrangement, after Forfeiture	95													706							(610)
Purchase of treasury stock,				$ (462)																			$ (462)
Common stock ($0.17 per share in 2019 and $0.18 per share in 2020)	(27,875)															(27,875)
Preferred stock(a)	(5,207)															(5,207)
Issuance of preferred stock	(208)									(208)
Stock-based compensation expense, net	3,502													3,502
Ending balance at Sep. 30, 2020	$ 4,045,433									$ 353,637		$ 1,752		$ 1,717,186		$ 2,424,992			$ 3,995		$ (456,129)
Cash dividends
Preferred Stock, Dividends, Per Share, Cash Paid						$ 0.3828125	$ 0.3359375	$ 0.3671875	$ 0.3515625