CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDERS' EQUITY - USD ($) shares in Thousands, $ in Thousands	Total	Cumulative Effect, Period of Adoption, Adjustment	Common Stock	Additional Paid in Capital	Retained Earnings	Retained Earnings Cumulative Effect, Period of Adoption, Adjustment	Accumulated Other Comprehensive Income (loss)	Treasury Stock
Beginning Balance (in shares) at Dec. 31, 2017			46,871					1,704
Beginning Balance at Dec. 31, 2017	$ 2,430,531	$ 3,076	$ 46,871	$ 591,721	$ 2,285,886	$ 3,076	$ (265,091)	$ (228,856)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	200,802				200,802
Cash dividends	(62,165)				(62,165)
Other comprehensive income (loss)	(75,994)						(75,994)
Settlement of warrants (in shares)								(412)
Settlement of warrants	(40)			(56,115)				$ 56,075
Shares issued under compensation plans (in shares)			377					(50)
Shares issued under compensation plans	42,899		$ 377	38,756				$ 3,766
Deferred compensation (in shares)								(10)
Deferred compensation	869			399				$ 470
Ending Balance (in shares) at Dec. 31, 2018			47,248					1,232
Ending Balance at Dec. 31, 2018	$ 2,539,978	(1,321)	$ 47,248	574,761	2,427,599	(1,321)	(341,085)	$ (168,545)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Accounting Standards Update [Extensible List]	us-gaap:AccountingStandardsUpdate201613Member
Net income	$ 461,466				461,466
Cash dividends	(62,828)				(62,828)
Other comprehensive income (loss)	(3,307)						(3,307)
Shares issued under compensation plans (in shares)			288					(46)
Shares issued under compensation plans	44,952		$ 288	42,092				$ 2,572
Deferred compensation (in shares)								(4)
Deferred compensation	380			127				$ 253
Ending Balance (in shares) at Dec. 31, 2019			47,536					1,182
Ending Balance at Dec. 31, 2019	2,979,320	$ (791)	$ 47,536	616,980	2,824,916	$ (791)	(344,392)	$ (165,720)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	335,324				335,324
Cash dividends	(63,221)				(63,221)
Other comprehensive income (loss)	47,094						47,094
Shares issued under compensation plans (in shares)			276					(44)
Shares issued under compensation plans	37,732		$ 276	35,223				$ 2,233
Deferred compensation (in shares)								(6)
Deferred compensation	999			102				$ 897
Ending Balance (in shares) at Dec. 31, 2020			47,812					1,132
Ending Balance at Dec. 31, 2020	$ 3,336,457		$ 47,812	$ 652,305	$ 3,096,228		$ (297,298)	$ (162,590)