Consolidated Statements of Changes in Shareholders' Equity (Unaudited) - USD ($) $ in Thousands	Total	Cumulative Effect, Period of Adoption, Adjustment	Cumulative Effect, Period of Adoption, Adjusted Balance	Common Stock	Common Stock Cumulative Effect, Period of Adoption, Adjusted Balance	Capital Surplus	Capital Surplus Cumulative Effect, Period of Adoption, Adjusted Balance	Retained Earnings	Retained Earnings Cumulative Effect, Period of Adoption, Adjustment	Retained Earnings Cumulative Effect, Period of Adoption, Adjusted Balance	Treasury Stock	Treasury Stock Cumulative Effect, Period of Adoption, Adjusted Balance	Accumulated Other Comprehensive Income (Loss)	Accumulated Other Comprehensive Income (Loss) Cumulative Effect, Period of Adoption, Adjusted Balance
Beginning Balance at Dec. 31, 2019	$ 657,983	$ (2,335)	$ 655,648	$ 47,619	$ 47,619	$ 170,309	$ 170,309	$ 539,253	$ (2,335)	$ 536,918	$ (105,038)	$ (105,038)	$ 5,840	$ 5,840
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	29,000							29,000
Other comprehensive income (loss)	21,620												21,620
Cash dividends declared	(9,200)							(9,200)
Stock-based compensation expense	1,009					1,009
Restricted awards granted	0					(1,154)					1,154
Exercise of stock options	122					(68)					190
Purchase of treasury shares	(12,971)										(12,971)
Ending balance at Mar. 31, 2020	685,228			47,619		170,096		556,718			(116,665)		27,460
Beginning Balance at Dec. 31, 2020	701,106			47,619		171,304		589,988			(139,038)		31,233
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	19,814							19,814
Other comprehensive income (loss)	(15,605)												(15,605)
Cash dividends declared	(9,406)							(9,406)
Stock-based compensation expense	1,153					1,153
Restricted awards granted	0					(464)					464
Exercise of stock options	385					(1,467)					1,852
Purchase of treasury shares	(5,762)										(5,762)
Ending balance at Mar. 31, 2021	$ 691,685			$ 47,619		$ 170,526		$ 600,396			$ (142,484)		$ 15,628