Consolidated Statement of Changes in Stockholders' Equity - USD ($) $ in Thousands		Total	Common Stock	Common Stock and Additional Paid-In Capital	Retained Earnings	Treasury Stock	AOCI, net of Tax
Beginning balance at Dec. 31, 2016		$ 3,427,741		$ 1,727,598	$ 2,187,676	$ (439,387)	$ (48,146)
Balance (in shares) at Dec. 31, 2016			144,167,451
Increase (Decrease) in Stockholders' Equity
Net income		505,624			505,624
Other comprehensive income (loss)		10,627					10,627
Net activity of common stock pursuant to various stock compensation plans and agreements		14,957		27,897		(12,940)
Net activity of common stock pursuant to various stock compensation plans and agreements (in shares)			375,609
Cash dividends on common stock		(116,998)			(116,998)
Ending balance at Dec. 31, 2017		3,841,951		1,755,495	2,576,302	(452,327)	(37,519)
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	[1]	0			6,656		(6,656)
Beginning balance at Dec. 31, 2017		3,841,951		1,755,495	2,576,302	(452,327)	(37,519)
Balance (in shares) at Dec. 31, 2017			144,543,060
Increase (Decrease) in Stockholders' Equity
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)
Balance (in shares) at Dec. 31, 2018			144,961,363
Increase (Decrease) in Stockholders' Equity
Cumulative effect of change in accounting principle related to marketable equity securities	[2]	(160)			(545)		385
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)
Balance (in shares) at Dec. 31, 2019			145,625,385

[1] 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 in the first quarter of 2018. Refer to Note 1 — Summary of Significant Accounting Policies to the Consolidated Financial Statements for additional information.

[2] 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 in the first quarter of 2018. 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.