CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDERS' EQUITY (Unaudited) - USD ($) $ in Thousands	Total	Impact of new accounting standard	Common Stock	Additional Paid-in Capital	Retained Earnings	Retained Earnings Impact of new accounting standard	Accumulated Other Comprehensive Income	Treasury Stock
Beginning Balance at Dec. 31, 2019	$ 1,191,998	$ (22,590)	$ 103,623	$ 399,944	$ 761,083	$ (22,590)	$ (11,670)	$ (60,982)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(3,136)				(3,136)
Other comprehensive income (loss), net of tax	21,123						21,123
Cash dividends declared	(32,972)				(32,972)
Treasury stock issued for restricted stock awards, net of forfeitures	(594)				(4,034)			3,440
Repurchase of common stock	(12,559)							(12,559)
Recognition of restricted stock compensation expense	845			845
Ending Balance at Sep. 30, 2020	$ 1,142,115		103,623	400,789	698,351		9,453	(70,101)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Accounting Standards Update [Extensible List]	ASU No. 2016-13
Beginning Balance at Dec. 31, 2019	$ 1,191,998	$ (22,590)	103,623	399,944	761,083	$ (22,590)	(11,670)	(60,982)
Ending Balance at Dec. 31, 2020	1,154,711		103,623	400,668	710,061		8,971	(68,612)
Beginning Balance at Jun. 30, 2020	1,135,777		103,623	400,417	692,240		9,232	(69,735)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	16,705				16,705
Other comprehensive income (loss), net of tax	221						221
Cash dividends declared	(10,960)				(10,960)
Forfeitures of restricted stock awards	0				366			(366)
Recognition of restricted stock compensation expense	372			372
Ending Balance at Sep. 30, 2020	$ 1,142,115		103,623	400,789	698,351		9,453	(70,101)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Accounting Standards Update [Extensible List]	ASU No. 2016-13
Beginning Balance at Dec. 31, 2020	$ 1,154,711		103,623	400,668	710,061		8,971	(68,612)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	87,866				87,866
Other comprehensive income (loss), net of tax	(10,000)						(10,000)
Cash dividends declared	(32,954)				(32,954)
Treasury stock issued for restricted stock awards, net of forfeitures	(302)				(2,599)			2,297
Recognition of restricted stock compensation expense	2,360			2,360
Ending Balance at Sep. 30, 2021	$ 1,201,681		103,623	403,028	762,374		(1,029)	(66,315)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Accounting Standards Update [Extensible List]	ASU No. 2016-13
Beginning Balance at Jun. 30, 2021	$ 1,188,733		103,623	402,053	746,472		3,605	(67,020)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	27,598				27,598
Other comprehensive income (loss), net of tax	(4,634)						(4,634)
Cash dividends declared	(10,991)				(10,991)
Treasury stock issued for restricted stock awards, net of forfeitures	0				(705)			705
Recognition of restricted stock compensation expense	975			975
Ending Balance at Sep. 30, 2021	$ 1,201,681		$ 103,623	$ 403,028	$ 762,374		$ (1,029)	$ (66,315)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Accounting Standards Update [Extensible List]	ASU No. 2016-13