Consolidated Statement of Changes in Stockholders' Equity - USD ($) $ in Thousands		Total	Cumulative Effect, Period of Adoption, Adjustment	Common Stock	Common Stock and Additional Paid-In Capital	Retained Earnings	Retained Earnings Cumulative Effect, Period of Adoption, Adjustment	Treasury Stock	AOCI, net of Tax	AOCI, net of Tax Cumulative Effect, Period of Adoption, Adjustment
Beginning balance at Dec. 31, 2017		$ 3,841,951			$ 1,755,495	$ 2,576,302		$ (452,327)	$ (37,519)
Beginning balance (Accounting Standards Update 2016-01) at Dec. 31, 2017	[1]		$ (160)				$ (545)			$ 385
Balance (in shares) at Dec. 31, 2017				144,543,060
Increase (Decrease) in Stockholders' Equity
Reclassification of tax effects in AOCI resulting from the new federal corporate income tax rate | Accounting Standards Update 2018-02		6,700								6,656
Ending balance (Accounting Standards Update 2016-01) at Jan. 01, 2018										385
Beginning balance at Dec. 31, 2017		3,841,951			1,755,495	2,576,302		(452,327)	(37,519)
Beginning balance (Accounting Standards Update 2016-01) at Dec. 31, 2017	[1]		(160)				(545)			$ 385
Balance (in shares) at Dec. 31, 2017				144,543,060
Increase (Decrease) in Stockholders' Equity
Reclassification of tax effects in AOCI resulting from the new federal corporate income tax rate | Accounting Standards Update 2018-02	[2]					6,656			(6,656)
Net income		703,701				703,701
Other comprehensive income (loss)		(14,384)							(14,384)
Net activity of common stock pursuant to various stock compensation plans and agreements		18,848			34,482			(15,634)
Net activity of common stock pursuant to various stock compensation plans and agreements (in shares)				418,303
Cash dividends on common stock		(125,982)				(125,982)
Ending balance at Dec. 31, 2018		4,423,974			1,789,977	3,160,132		(467,961)	(58,174)
Ending balance (Accounting Standards Update 2016-02) at Dec. 31, 2018	[3]		10,510				10,510
Balance (in shares) at Dec. 31, 2018				144,961,363
Increase (Decrease) in Stockholders' Equity
Net income		674,035				674,035
Other comprehensive income (loss)		39,766							39,766
Warrants exercised		4,443			1,711			2,732
Warrants exercised (in shares)				180,226
Net activity of common stock pursuant to various stock compensation plans and agreements		20,189			34,824			(14,635)
Net activity of common stock pursuant to various stock compensation plans and agreements (in shares)				483,796
Cash dividends on common stock		(155,300)				(155,300)
Ending balance at Dec. 31, 2019		5,017,617			1,826,512	3,689,377		(479,864)	(18,408)
Ending balance (Accounting Standards Update 2016-13) at Dec. 31, 2019	[4]		$ (97,967)				$ (97,967)
Balance (in shares) at Dec. 31, 2019				145,625,385
Increase (Decrease) in Stockholders' Equity
Net income		567,797				567,797
Other comprehensive income (loss)		62,733							62,733
Net activity of common stock pursuant to various stock compensation plans and agreements		23,754			32,007			(8,253)
Net activity of common stock pursuant to various stock compensation plans and agreements (in shares)				411,526
Repurchase of common stock pursuant to the Stock Repurchase Program		(145,966)						(145,966)
Repurchase of common stock pursuant to the Stock Repurchase Program (in shares)				(4,471,682)
Cash dividends on common stock		(158,793)				(158,793)
Ending balance at Dec. 31, 2020		$ 5,269,175			$ 1,858,519	$ 4,000,414		$ (634,083)	$ 44,325
Balance (in shares) at Dec. 31, 2020				141,565,229
Increase (Decrease) in Stockholders' Equity
Accounting Standards Update [Extensible List]		us-gaap:AccountingStandardsUpdate201613Member

[1] Represents the impact of the adoption of Accounting Standards Update (“ASU”) 2016-01, Financial Instruments — Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities on January 1, 2018.

[2] Represents amounts reclassified from AOCI to retained earnings due to the early adoption of ASU 2018-02, Income Statement — Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income on January 1, 2018.

[3] Represents the impact of the adoption of ASU 2016-02, Leases (Topic 842) and subsequent related ASUs on January 1, 2019.

[4] Represents the impact of the adoption of ASU 2016-13, Financial Instruments — Credit Losses (Topic 326) on January 1, 2020. Refer to Note 1 — Summary of Significant Accounting Policies to the Consolidated Financial Statements in this Annual Report on Form 10-K (“this Form 10-K”) for additional information.