Condensed Consolidated Statements of Changes in Shareholders' Equity - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive (Loss) Income [Member]	Treasury Stock [Member]
Beginning balance at Dec. 31, 2018	$ 624,133	$ 157,784	$ 292,401	$ 248,167	$ (28,416)	$ (45,803)
Beginning balance, shares at Dec. 31, 2018		29,270,852
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	16,079	$ 0	0	16,079	0	0
Other comprehensive income, net of income tax	4,095	0	0	0	4,095	0
Cash dividends declared	(5,853)	0	0	(5,853)	0	0
Stock-based compensation	574	0	574	0	0	0
Stock issued under dividend reinvestment and employee stock purchase plans	571	$ 0	30	0	0	541
Stock issued under dividend reinvestment and employee stock purchase plans, shares		25,743
Exercise of stock options	521	$ 0	(91)	0	0	612
Exercise of stock options, shares		30,500
Cancellations of performance-based restricted stock awards	0	$ 0	341	0	0	(341)
Cancellation of performance-based restricted stock awards, shares		(17,349)
Purchases of treasury stock	(950)	$ 0	0	0	0	(950)
Purchases of treasury stock, shares		(37,244)
Ending balance at Mar. 31, 2019	$ 637,606	$ 157,784	293,255	256,746	(24,238)	(45,941)
Ending balance, shares at Mar. 31, 2019		29,272,502
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cash dividends declared, per share	$ 0.20
Beginning balance at Dec. 31, 2019	$ 675,122	$ 157,784	294,999	288,803	(21,730)	(44,734)
Beginning balance, shares at Dec. 31, 2019		29,334,629
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	838	$ 0	0	838	0	0
Other comprehensive income, net of income tax	(4,135)	0	0	0	(4,135)	0
Cash dividends declared	(5,866)	0	0	(5,866)	0	0
Stock-based compensation	411	0	424	(13)	0	0
Stock issued under dividend reinvestment and employee stock purchase plans	572	$ 0	(49)	0	0	621
Stock issued under dividend reinvestment and employee stock purchase plans, shares		26,045
Vesting of restricted stock unit awards	0	$ 0	(346)	0	0	346
Vesting of restricted stock unit awards, shares		17,035
Exercise of stock options	$ 94	$ 0	(7)	0	0	101
Exercise of stock options, shares	5,000	5,000
Cancellations of performance-based restricted stock awards	$ 0	$ 0	418	0	0	(418)
Cancellation of performance-based restricted stock awards, shares		(14,777)
Purchases of treasury stock	(4,438)	$ 0	0	0	0	(4,438)
Purchases of treasury stock, shares		(203,150)
Ending balance at Mar. 31, 2020	$ 651,551	$ 157,784	$ 295,439	$ 272,478	$ (25,628)	$ (48,522)
Ending balance, shares at Mar. 31, 2020		29,164,782
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cash dividends declared, per share	$ 0.20