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]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative Effect of New Accounting Principle in Period of Adoption | Accounting Standards Update 2016-01		$ 0	$ 0	$ 0	$ 433	$ (433)		$ 0
Cumulative Effect of New Accounting Principle in Period of Adoption | Accounting Standards Update 2018-02		0	0	0	3,921	(3,921)		0
Beginning balance at Dec. 31, 2017		603,374	$ 157,784	290,133	216,761	(17,771)		(43,533)
Beginning balance, shares at Dec. 31, 2017			29,334,859
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		12,850	$ 0	0	12,850	0		0
Other comprehensive income, net of income tax		(4,666)	0	0	0	(4,666)		0
Cash dividends declared ($0.20 per share)		(5,868)	0	0	(5,868)	0		0
Stock issued under dividend reinvestment and employee stock purchase plans		569	$ 0	44	0	0		525
Stock issued under dividend reinvestment and employee stock purchase plans, shares			20,253
Exercise of stock options		268	$ 0	(9)	0	0		277
Exercise of stock options, shares			14,158
Stock-based compensation		847	$ 0	847	0	0		0
Purchases of treasury stock		(655)	$ 0	0	0	0		(655)
Purchases of treasury stock, shares			(23,539)
Restricted stock awards granted, net of cancellations		0	$ 0	(920)	0	0		920
Restricted stock awards granted, net of cancellations, shares			46,203
Ending balance at Mar. 31, 2018		606,719	$ 157,784	290,095	228,097	(26,791)		(42,466)
Ending balance, shares at Mar. 31, 2018			29,391,934
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative Effect of New Accounting Principle in Period of Adoption | Accounting Standards Update 2016-02	[1]	(1,525)	$ 0	0	(1,525)	0		0
Cumulative Effect of New Accounting Principle in Period of Adoption | Accounting Standards Update 2017-12	[1]	0	0	0	(83)	83	[2]	0
Cumulative Effect of New Accounting Principle in Period of Adoption | Accounting Standards Update 2017-08	[1]	(39)	0	0	(39)	0		0
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 ($0.20 per share)		(5,853)	0	0	(5,853)	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	30,500
Stock-based compensation		$ 574	$ 0	574	0	0		0
Purchases of treasury stock		(950)	$ 0	0	0	0		(950)
Purchases of treasury stock, shares			(37,244)
Cancellations of performance-based restricted stock awards		0	$ 0	341	0	0		(341)
Cancellations of performance-based restricted stock awards, shares			(17,349)
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

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

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