Consolidated Statements of Changes in Stockholders' Equity - USD ($) $ in Thousands		Total	Cumulative Effect, Period of Adoption, Adjustment [Member]	Cumulative Effect, Period of Adoption, Adjusted Balance [Member]	Performance/Service Based RSAs, RSA, [Member]	Board Authorized Purchase Program [Member]	Preferred Equity	Preferred Equity Cumulative Effect, Period of Adoption, Adjusted Balance [Member]	Common Stock [Member]	Common Stock [Member] Cumulative Effect, Period of Adoption, Adjusted Balance [Member]	Surplus	Surplus Cumulative Effect, Period of Adoption, Adjusted Balance [Member]	Retained Earnings	Retained Earnings Cumulative Effect, Period of Adoption, Adjustment [Member]	Retained Earnings Cumulative Effect, Period of Adoption, Adjusted Balance [Member]	Retained Earnings Series C Preferred Stock	Retained Earnings Series D Preferred Stock	Retained Earnings Series E Preferred Stock	Retained Earnings Series F Preferred Stock [Member]	Accumulated Other Comprehensive Income (Loss)	Accumulated Other Comprehensive Income (Loss) Cumulative Effect, Period of Adoption, Adjusted Balance [Member]	Treasury Stock	Treasury Stock Cumulative Effect, Period of Adoption, Adjusted Balance [Member]	Treasury Stock Performance/Service Based RSAs, RSA, [Member]	Treasury Stock Board Authorized Purchase Program [Member]
Beginning balance at Dec. 31, 2017		$ 3,237,443					$ 159,929		$ 1,618		$ 1,338,722		$ 1,934,696							$ (62,758)		$ (134,764)
Preferred stock shares outstanding, beginning balance (in shares) at Dec. 31, 2017							165,000
Common stock shares outstanding, beginning balance (in shares) at Dec. 31, 2017									161,752,000
Comprehensive income:
Net income		333,562											333,562
Other Comprehensive Income, Other, Net of Tax		(48,476)																		(48,476)
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification		(13,738)																		(13,738)
Other comprehensive income (loss)		(62,214)																		(62,214)
Comprehensive income		271,348
Issuance of preferred stock		97,315					$ 97,315
Common stock issued:
Stock-based compensation plans, net		18,408									(7,116)		15,096									10,428
Common Stock Issued During Period, Shares, Acquisitions									13,705,000
Issuance of treasury stock for acquisition		488,408							$ 137		396,975											91,296
Purchase of common stock returned to authorized but unissued, shares									(1,357,000)
Purchase of common stock returned to authorized but unissued, amount		(33,075)							$ (14)		(33,061)
Purchase of Treasury Stock					$ (7,148)	$ (206,450)																		$ (7,148)	$ (206,450)
Cash dividends
Common stock dividends		(105,519)											(105,519)
Preferred stock dividends	[1]	(10,784)											(10,784)
Issuance of preferred stock							100,000
Issuance of preferred stock		97,315					$ 97,315
Purchase of Preferred Stock Repurchased During Period, Shares							1,000
Purchase of stock, value		537					$ 528						8
Common Stock Shares from Warrant Exercises									1,116,000
Proceeds from Warrant Exercises		1							$ (11)		12
Stock-based compensation expense, net		17,107									17,107
Tax Act Reclassification		13,654											13,654
Change in Accounting Principal		84											84
Other		632											632
Ending balance at Dec. 31, 2018		3,780,888					$ 256,716		$ 1,752		1,712,615		2,181,414							(124,972)		(246,638)
Preferred stock shares outstanding, ending balance (in shares) at Dec. 31, 2018							264,000
Common stock shares outstanding, ending balance (in shares) at Dec. 31, 2018									175,216,000
Cash dividends
Preferred Stock, Dividends, Per Share, Cash Paid																$ 1.53125	$ 1.34375	$ 0.322309
Net income		326,790											326,790
Other comprehensive income (loss)		91,789																		91,789
Comprehensive income		418,579
Stock-based compensation plans, net		11,216									(21,038)											32,254
Purchase of Treasury Stock					(8,592)	(177,484)																		(8,592)	(177,484)
Common stock dividends		(111,804)											(111,804)
Preferred stock dividends	[2]	(15,202)											(15,202)
Stock-based compensation expense, net		24,854									24,854
Other		(331)											(331)
Ending 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)
Ending balance (Accounting Standards Update 2016-13 [Member]) at Dec. 31, 2019			$ (98,337)											$ (98,337)
Preferred stock shares outstanding, ending balance (in shares) at Dec. 31, 2019							264,000	264,000
Common stock shares outstanding, ending balance (in shares) at Dec. 31, 2019		157,171,247							175,216,000	175,216,000
Cash dividends
Preferred Stock, Dividends, Per Share, Cash Paid																1.53125	1.34375	1.46875
Net income		$ 306,771											306,771
Other comprehensive income (loss)		45,801																		45,801
Comprehensive income		352,572
Issuance of preferred stock		96,796					$ 96,796
Stock-based compensation plans, net		3,966									(17,663)											21,629
Purchase of Treasury Stock					$ (6,113)	$ (71,255)																		$ (6,113)	$ (71,255)
Common stock dividends		(112,023)											(112,023)
Preferred stock dividends	[3]	(18,358)											(18,358)
Issuance of preferred stock							100,000
Issuance of preferred stock		96,796					$ 96,796
Stock-based compensation expense, net		21,561									21,561
Ending balance at Dec. 31, 2020		$ 4,090,933					$ 353,512		$ 1,752		$ 1,720,329		$ 2,458,920							$ 12,618		$ (456,198)
Preferred stock shares outstanding, ending balance (in shares) at Dec. 31, 2020							364,000
Common stock shares outstanding, ending balance (in shares) at Dec. 31, 2020		153,540,224							175,216,000
Cash dividends
Preferred Stock, Dividends, Per Share, Cash Paid																$ 1.53125	$ 1.34375	$ 1.46875	$ 0.7881181

[1] (a) Series C, $1.53125 per share; Series D, $1.34375 per share; and Series E, $0.322309 per share.

[2] (b) Series C, $1.53125 per share; Series D, $1.34375 per share; and Series E, $1.46875 per share.

[3] (c) Series C, $1.53125 per share; Series D, $1.34375 per share; Series E, $1.46875 per share; and Series F, $0.7881181 per share.