Consolidated Statements of Changes in Stockholders' Equity (Unaudited) - USD ($) $ in Thousands	Total	Cumulative Effect, Period Of Adoption, Adjustment	Performance/Service Based RSAs, RSA,	Board Authorized Purchase Program [Member]	Series C Preferred Stock	Series D Preferred Stock	Series E Preferred Stock	Preferred Equity	Preferred Equity Cumulative Effect, Period Of Adoption, Adjustment	Common Stock	Common Stock Cumulative Effect, Period Of Adoption, Adjustment	Surplus	Surplus Cumulative Effect, Period Of Adoption, Adjustment	Retained Earnings	Retained Earnings Cumulative Effect, Period Of Adoption, Adjustment	Retained Earnings Series F Preferred Stock	Accumulated Other Comprehensive Income (Loss)	Accumulated Other Comprehensive Income (Loss) Cumulative Effect, Period Of Adoption, Adjustment	Treasury Stock	Treasury Stock Cumulative Effect, Period Of Adoption, Adjustment	Treasury Stock Performance/Service Based RSAs, RSA,	Treasury Stock Board Authorized Purchase Program [Member]
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)
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)		0					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, 2020	4,090,933							353,512		1,752		1,720,329		2,458,920			12,618		(456,198)
Comprehensive income
Net income	94,301													94,301
Other comprehensive income (loss)	(16,811)																(16,811)
Comprehensive income	77,490
Common stock issued
Shares Issued, Value, Share-based Payment Arrangement, after Forfeiture	10,556											(16,986)							27,542
Purchase of treasury stock,			$ (3,593)	$ (17,973)																	$ (3,593)	$ (17,973)
Cash dividends
Common stock ($0.17 per share in 2019 and $0.18 per share in 2020)	(27,870)													(27,870)
Preferred stock(a)	(5,207)													(5,207)
Stock-based compensation expense, net	3,444											3,444
Ending balance at Mar. 31, 2021	$ 4,127,780							$ 353,512		$ 1,752		$ 1,706,786		$ 2,520,144			$ (4,193)		$ (450,222)
Cash dividends
Preferred Stock, Dividends, Per Share, Cash Paid					$ 0.3828125	$ 0.3359375	$ 0.3671875									$ 0.3515625