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, 2017		$ 3,841,951		$ 1,755,495	$ 2,576,302	$ (452,327)	$ (37,519)
Beginning 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)
Beginning balance (in shares) at Dec. 31, 2017			144,543,060
Increase (Decrease) in Stockholders' Equity
Net income		530,683			530,683
Other comprehensive income (loss)		(46,046)					(46,046)
Net activity of common stock pursuant to various stock compensation plans and agreements		10,726		26,228		(15,502)
Net activity of common stock pursuant to various stock compensation plans and agreements (in shares)			386,371
Cash dividends on common stock		(92,304)			(92,304)
Ending balance at Sep. 30, 2018		4,244,850		1,781,723	3,020,792	(467,829)	(89,836)
Ending balance (in shares) at Sep. 30, 2018			144,929,431
Increase (Decrease) in Stockholders' Equity
Cumulative effect of a change in accounting principle	[2]	(160)			(545)		385
Beginning balance at Jun. 30, 2018		4,114,284		1,770,038	2,883,201	(467,488)	(71,467)
Beginning balance (in shares) at Jun. 30, 2018			144,904,629
Increase (Decrease) in Stockholders' Equity
Net income		171,302			171,302
Other comprehensive income (loss)		(18,369)					(18,369)
Net activity of common stock pursuant to various stock compensation plans and agreements		11,344		11,685		(341)
Net activity of common stock pursuant to various stock compensation plans and agreements (in shares)			24,802
Cash dividends on common stock		(33,711)			(33,711)
Ending balance at Sep. 30, 2018		4,244,850		1,781,723	3,020,792	(467,829)	(89,836)
Ending balance (in shares) at Sep. 30, 2018			144,929,431
Beginning balance at Dec. 31, 2018		4,423,974		1,789,977	3,160,132	(467,961)	(58,174)
Beginning balance (in shares) at Dec. 31, 2018			144,961,363
Increase (Decrease) in Stockholders' Equity
Net income		485,820			485,820
Other comprehensive income (loss)		57,207					57,207
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		11,348		25,578		(14,230)
Net activity of common stock pursuant to various stock compensation plans and agreements (in shares)			426,123
Cash dividends on common stock		(114,796)			(114,796)
Ending balance at Sep. 30, 2019		4,882,664		1,817,266	3,545,824	(479,459)	(967)
Ending balance (in shares) at Sep. 30, 2019			145,567,712
Beginning balance at Jun. 30, 2019		4,734,593		1,809,062	3,414,901	(479,398)	(9,972)
Beginning balance (in shares) at Jun. 30, 2019			145,546,569
Increase (Decrease) in Stockholders' Equity
Net income		171,416			171,416
Other comprehensive income (loss)		9,005					9,005
Net activity of common stock pursuant to various stock compensation plans and agreements		8,143		8,204		(61)
Net activity of common stock pursuant to various stock compensation plans and agreements (in shares)			21,143
Cash dividends on common stock		(40,493)			(40,493)
Ending balance at Sep. 30, 2019		$ 4,882,664		$ 1,817,266	$ 3,545,824	$ (479,459)	$ (967)
Ending balance (in shares) at Sep. 30, 2019			145,567,712

[1] Represents amounts reclassified from AOCI to retained earnings due to 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.

[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.