Consolidated Statements of Changes in Shareholders' Equity - USD ($) $ in Thousands	Total	Cumulative Effect, Period of Adoption, Adjustment [Member]	Common Stock [Member]	Common Stock [Member] Cumulative Effect, Period of Adoption, Adjustment [Member]	Additional Paid-in Capital [Member]	Additional Paid-in Capital [Member] Cumulative Effect, Period of Adoption, Adjustment [Member]	Retained Earnings [Member]	Retained Earnings [Member] Cumulative Effect, Period of Adoption, Adjustment [Member]		Accumulated Other Comprehensive (Loss) Income [Member]	Accumulated Other Comprehensive (Loss) Income [Member] Cumulative Effect, Period of Adoption, Adjustment [Member]		Treasury Stock [Member]	Treasury Stock [Member] Cumulative Effect, Period of Adoption, Adjustment [Member]
Beginning balance at Dec. 31, 2017	$ 603,374		$ 157,784		$ 290,133		$ 216,761			$ (17,771)			$ (43,533)
Beginning balance (Accounting Standards Update 2016-01 [Member]) at Dec. 31, 2017		$ 0		$ 0		$ 0		$ 433			$ (433)			$ 0
Beginning balance (Accounting Standards Update 2018-02 [Member]) at Dec. 31, 2017		0		0		0		3,921			(3,921)
Beginning balance, shares at Dec. 31, 2017			29,334,859
Increase (Decrease) in Stockholders' Equity [Roll Forward]
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	(23,492)		0		0		(23,492)			0			0
Stock issued under dividend reinvestment and employee stock purchase plans	2,295		$ 0		152		1			0			2,142
Stock issued under dividend reinvestment and employee stock purchase plans, shares			84,466
Exercise of stock options	1,131		$ 0		(43)		0			0			1,174
Exercise of stock options, shares			59,750
Restricted stock awards granted, net of cancellations	0		$ 0		(398)		0			0			398
Restricted stock awards granted, net of cancellations, shares			25,754
Treasury Stock, Value, Acquired, Cost Method	(5,984)		$ 0		0		0			0			(5,984)
Purchases of treasury stock, shares			(233,977)
Ending balance at Dec. 31, 2018	$ 624,133		$ 157,784		292,401		248,167			(28,416)			(45,803)
Ending balance (Accounting Standards Update 2016-02 [Member]) at Dec. 31, 2018		(1,525)		0		0		(1,525)			0			0
Ending balance (Accounting Standards Update 2017-12 [Member]) at Dec. 31, 2018		0		0		0		(83)			83			0
Ending balance (Accounting Standards Update 2017-08 [Member]) at Dec. 31, 2018		(39)		0		0		(39)			0			0
Ending balance, shares at Dec. 31, 2018			29,270,852
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cash dividends declared, per share	$ 0.80
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	(23,437)		0		0		(23,437)			0			0
Stock-based compensation	2,277		0		2,277		0			0			0
Stock issued under dividend reinvestment and employee stock purchase plans	2,233		$ 0		162		1			0			2,070
Stock issued under dividend reinvestment and employee stock purchase plans, shares			90,669
Exercise of stock options	1,203		$ 0		(182)		0			0			1,385
Exercise of stock options, shares			69,038
Cancellations of performance-based restricted stock awards	0		$ 0		341		0			0			(341)
Cancellations of performance-based restricted stock awards, shares			(17,349)
Treasury Stock, Value, Acquired, Cost Method	(2,045)		$ 0		0		0			0			(2,045)
Purchases of treasury stock, shares			78,581
Ending balance at Dec. 31, 2019	$ 675,122		$ 157,784		294,999		288,803			(21,730)			(44,734)
Ending balance (Accounting Standards Update 2016-13) at Dec. 31, 2019		$ (11,047)		$ 0		$ 0		$ (11,284)	[1]		$ 237	[2]		$ 0
Ending balance, shares at Dec. 31, 2019			29,334,629
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cash dividends declared, per share	$ 0.80
Net income	$ 46,916		$ 0		0		46,916			0			0
Other comprehensive income (loss), net of income tax (benefit)	(651)		0		0		0			(651)			0
Cash dividends declared	(17,522)		0		0		(17,522)			0			0
Stock-based compensation	1,353		0		1,367		(14)			0			0
Stock issued under dividend reinvestment and employee stock purchase plans	2,369		$ 0		(197)		0			0			2,566
Stock issued under dividend reinvestment and employee stock purchase plans, shares			140,721
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	$ 384		$ 0		(55)		0			0			439
Exercise of stock options, shares	21,500		21,500
Cancellations of performance-based restricted stock awards	$ 0		$ 0		418		0			0			(418)
Cancellations of performance-based restricted stock awards, shares			(14,777)
Treasury Stock, Value, Acquired, Cost Method	(4,452)		$ 0		0		0			0			(4,452)
Purchases of treasury stock, shares			204,056
Ending balance at Dec. 31, 2020	$ 692,472		$ 157,784		$ 296,186		$ 306,899			$ (22,144)			$ (46,253)
Ending balance, shares at Dec. 31, 2020			29,295,052
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cash dividends declared, per share	$ 0.60

[1] (1) See Note 1, "Summary of Significant Accounting Policies - Accounting Pronouncements Adopted in 2020" for additional information.

[2] (1) See Note 1, "Summary of Significant Accounting Policies - Accounting Pronouncements Adopted in 2020" for additional information.