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, 2016	$ 505,209	$ 144,559	$ 230,494	$ 194,516		$ (19,454)		$ (44,906)
Beginning balance, shares at Dec. 31, 2016		26,589,353
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	44,094	$ 0	0	44,094		0		0
Other comprehensive income (loss), net of income tax (benefit)	1,683	0	0	0		1,683		0
Cash dividends declared ($0.80 per share)	(21,849)	$ 0	0	(21,849)		0		0
Stock issued under dividend reinvestment and employee stock purchase plans, shares		82,694
Stock issued under dividend reinvestment and employee stock purchase plans	2,413	$ 0	181	0		0		2,232
Issuance of common stock, public offering, shares		2,645,000
Issuance of common stock, public offering	70,501	$ 13,225	57,276	0		0		0
Exercise of stock options, shares		92,370
Exercise of stock options	1,676	$ 0	(119)	0		0		1,795
Stock-based compensation	3,166	$ 0	3,166	0		0		0
Purchases of treasury stock, shares		(119,798)
Purchases of treasury stock	(3,519)	$ 0	0	0		0		(3,519)
Restricted stock awards granted, net of cancellations, shares		45,240
Cancellations of performance-based restricted stock awards	0	$ 0	(865)	0		0		865
Ending balance at Dec. 31, 2017	$ 603,374	$ 157,784	290,133	216,761		(17,771)		(43,533)
Ending balance, shares at Dec. 31, 2017		29,334,859
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cash dividends declared, per share	$ 0.80
Cumulative effect of new accounting principle in period of adoption | Accounting Standards Update 2016-01 [Member]	$ 0	$ 0	0	433		(433)		0
Cumulative effect of new accounting principle in period of adoption | Accounting Standards Update 2018-02 [Member]	0	0	0	3,921		(3,921)
Net income	50,543	0	0	50,543		0		0
Other comprehensive income (loss), net of income tax (benefit)	(6,291)	0	0	0		(6,291)		0
Cash dividends declared ($0.80 per share)	(23,492)	$ 0	0	(23,492)		0		0
Stock issued under dividend reinvestment and employee stock purchase plans, shares		84,466
Stock issued under dividend reinvestment and employee stock purchase plans	2,295	$ 0	152	1		0		2,142
Exercise of stock options, shares		59,750
Exercise of stock options	1,131	$ 0	(43)	0		0		1,174
Stock-based compensation	2,557	$ 0	2,557	0		0		0
Purchases of treasury stock, shares		(233,977)
Purchases of treasury stock	(5,984)	$ 0	0	0		0		(5,984)
Restricted stock awards granted, net of cancellations, shares		25,754
Cancellations of performance-based restricted stock awards	0	$ 0	(398)	0		0		398
Ending balance at Dec. 31, 2018	$ 624,133	$ 157,784	292,401	248,167		(28,416)		(45,803)
Ending balance, shares at Dec. 31, 2018		29,270,852
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cash dividends declared, per share	$ 0.80
Cumulative effect of new accounting principle in period of adoption | Accounting Standards Update 2016-02 [Member]	$ (1,525)	$ 0	0	(1,525)	[1]	0		0
Cumulative effect of new accounting principle in period of adoption | Accounting Standards Update 2017-12 [Member]	0	0	0	(83)	[1]	83	[1]	0
Cumulative effect of new accounting principle in period of adoption | Accounting Standards Update 2017-08 [Member]	(39)	0	0	(39)	[1]	0		0
Net income	65,719	0	0	65,719		0		0
Other comprehensive income (loss), net of income tax (benefit)	6,603	0	0	0		6,603		0
Cash dividends declared ($0.80 per share)	(23,437)	$ 0	0	(23,437)		0		0
Stock issued under dividend reinvestment and employee stock purchase plans, shares		90,669
Stock issued under dividend reinvestment and employee stock purchase plans	$ 2,233	$ 0	162	1		0		2,070
Exercise of stock options, shares	69,038	69,038
Exercise of stock options	$ 1,203	$ 0	(182)	0		0		1,385
Stock-based compensation	2,277	$ 0	2,277	0		0		0
Purchases of treasury stock, shares		(78,581)
Purchases of treasury stock	(2,045)	$ 0	0	0		0		(2,045)
Restricted stock awards granted, net of cancellations, shares		(17,349)
Cancellations of performance-based restricted stock awards	0	$ 0	341	0		0		(341)
Ending balance at Dec. 31, 2019	$ 675,122	$ 157,784	$ 294,999	$ 288,803		$ (21,730)		$ (44,734)
Ending balance, shares at Dec. 31, 2019		29,334,629
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cash dividends declared, per share	$ 0.80

[1] (1) See Note 1, "Summary of Significant Accounting Policies - Accounting Pronouncements Adopted in 2019" for additional information.