Consolidated Statements Of Changes In Stockholders' Equity - USD ($) $ in Thousands	Common Stock [Member]	Surplus [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]		Total
Balance (in shares) at Dec. 31, 2016	23,699,107
Balance at Dec. 31, 2016	$ 2,370	$ 101,738	$ 203,326	$ (1,604)		$ 305,830
Net income			27,556			27,556
Other comprehensive income (loss)				2,777		2,777
Shares withheld upon the vesting and conversion of RSUs (in shares)	(19,339)
Shares withheld upon the vesting and conversion of RSUs	$ (2)	(525)				(527)
Common stock issued under stock compensation plans (in shares)	127,347
Common stock issued under stock compensation plans	$ 13	632				645
Common stock issued under dividend reinvestment and stock purchase plan (in shares)	575,672
Common stock issued under dividend reinvestment and stock purchase plan	$ 57	15,115				15,172
Stock-based compensation		1,925				1,925
Cash dividends declared			(10,421)			(10,421)
Balance (in shares) at Sep. 30, 2017	24,382,787
Balance at Sep. 30, 2017	$ 2,438	118,885	220,461	1,173		342,957
Balance (in shares) at Dec. 31, 2017	24,668,390
Balance at Dec. 31, 2017	$ 2,467	127,122	224,315	546		354,450
Net income			31,483			31,483
Other comprehensive income (loss)				(11,737)		(11,737)
Reclassification of stranded tax effects upon the adoption of ASU 2018-02			277	(277)	[1]
Shares tendered upon the exercise of stock options	$ (1)	(365)				$ (366)
Shares tendered upon the exercise of stock options (in shares)	(14,549)
Shares tendered upon the exercise of stock options (in shares)						48,158
Shares withheld upon the vesting and conversion of RSUs (in shares)	(27,194)
Shares withheld upon the vesting and conversion of RSUs	$ (3)	(764)				$ (767)
Common stock issued under stock compensation plans (in shares)	156,514
Common stock issued under stock compensation plans	$ 15	551				566
Common stock issued under dividend reinvestment and stock purchase plan (in shares)	639,834
Common stock issued under dividend reinvestment and stock purchase plan	$ 64	16,953				17,017
Stock-based compensation		1,526				1,526
Cash dividends declared			(11,902)			(11,902)
Balance (in shares) at Sep. 30, 2018	25,422,995
Balance at Sep. 30, 2018	$ 2,542	$ 145,023	$ 244,173	$ (11,468)		$ 380,270

[1] The adoption of Accounting Standards Update ("ASU") 2018-02 "Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income" in the first quarter of 2018 allowed the Corporation to reclassify certain stranded tax effects arising from the enactment of the Tax Cuts and Jobs Act ("Tax Act") in December 2017 from accumulated other comprehensive income to retained earnings. See "Note 11 - Adoption of New Accounting Standards" for more information regarding the effects of adopting ASU 2018-02.