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
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)
Net income		187,032			187,032
Other comprehensive income/loss		(12,014)					(12,014)
Net activity of common stock pursuant to various stock compensation plans and agreements		(8,788)		6,158		(14,946)
Net activity of common stock pursuant to various stock compensation plans and agreements (in shares)			329,465
Cash dividends on common stock		(29,266)			(29,266)
Ending balance at Mar. 31, 2018		3,978,755		1,761,653	2,740,179	(467,273)	(55,804)
Ending balance (in shares) at Mar. 31, 2018			144,872,525
Increase (Decrease) in Stockholders' Equity
Cumulative effect of a change in accounting principle	[2]	(160)			(545)		385
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		164,024			164,024
Other comprehensive income/loss		25,191					25,191
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		(6,600)		7,436		(14,036)
Net activity of common stock pursuant to various stock compensation plans and agreements (in shares)			359,712
Cash dividends on common stock		(33,770)			(33,770)
Ending balance at Mar. 31, 2019		$ 4,591,930		$ 1,799,124	$ 3,305,054	$ (479,265)	$ (32,983)
Ending balance (in shares) at Mar. 31, 2019			145,501,301

[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.

[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.