CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDERS' EQUITY - 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 (Loss) 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	13,231				13,231
Other comprehensive income, net of tax	17,342						17,342
Cash dividends declared	(11,051)				(11,051)
Treasury stock issued for restricted stock awards, net of forfeitures	(563)				53			(616)
Repurchase of common stock (411,430 shares)	(12,559)							(12,559)
Recognition of restricted stock compensation expense	443			443
Ending Balance at Mar. 31, 2020	1,176,251		103,623	400,387	740,726		5,672	(74,157)
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)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	31,902				31,902
Other comprehensive income, net of tax	(7,910)						(7,910)
Cash dividends declared	(10,975)				(10,975)
Treasury stock issued for restricted stock awards, net of forfeitures	(135)				730			(865)
Recognition of restricted stock compensation expense	685			685
Ending Balance at Mar. 31, 2021	$ 1,168,278		$ 103,623	$ 401,353	$ 731,718		$ 1,061	$ (69,477)