Consolidated Statements Of Changes In Stockholders' Equity - USD ($) $ in Thousands	Common Stock [Member]	Surplus [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Loss [Member]	Total
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			11,111		11,111
Other comprehensive income (loss)				(8,186)	(8,186)
Reclassification of stranded tax effects upon the adoption of ASU 2018-02			277	(277)
Shares withheld upon the vesting and conversion of RSUs (in shares)	(25,321)
Shares withheld upon the vesting and conversion of RSUs	$ (3)	(719)			(722)
Common stock issued under stock compensation plans (in shares)	112,237
Common stock issued under stock compensation plans	$ 11	101			112
Common stock issued under dividend reinvestment and stock purchase plan (in shares)	269,361
Common stock issued under dividend reinvestment and stock purchase plan	$ 27	7,292			7,319
Stock-based compensation		1,128			1,128
Cash dividends declared			(3,766)		(3,766)
Balance (in shares) at Mar. 31, 2018	25,024,667
Balance at Mar. 31, 2018	$ 2,502	134,924	231,937	(7,917)	361,446
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
Other comprehensive income (loss)					(11,737)
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
Balance (in shares) at Mar. 31, 2018	25,024,667
Balance at Mar. 31, 2018	$ 2,502	134,924	231,937	(7,917)	361,446
Net income			10,315		10,315
Other comprehensive income (loss)				(2,446)	(2,446)
Shares withheld upon the vesting and conversion of RSUs (in shares)	(414)
Shares withheld upon the vesting and conversion of RSUs		(11)			(11)
Common stock issued under stock compensation plans (in shares)	6,663
Common stock issued under stock compensation plans	$ 1	71			72
Common stock issued under dividend reinvestment and stock purchase plan (in shares)	322,420
Common stock issued under dividend reinvestment and stock purchase plan	$ 32	8,503			8,535
Stock-based compensation		133			133
Cash dividends declared			(3,805)		(3,805)
Balance (in shares) at Jun. 30, 2018	25,353,336
Balance at Jun. 30, 2018	$ 2,535	143,620	238,447	(10,363)	374,239
Net income			10,057		10,057
Other comprehensive income (loss)				(1,105)	(1,105)
Shares tendered upon the exercise of stock options	$ (1)	(365)			(366)
Shares tendered upon the exercise of stock options (in shares)	(14,549)
Shares withheld upon the vesting and conversion of RSUs (in shares)	(1,459)
Shares withheld upon the vesting and conversion of RSUs		(34)			(34)
Common stock issued under stock compensation plans (in shares)	37,614
Common stock issued under stock compensation plans	$ 3	379			382
Common stock issued under dividend reinvestment and stock purchase plan (in shares)	48,053
Common stock issued under dividend reinvestment and stock purchase plan	$ 5	1,158			1,163
Stock-based compensation		265			265
Cash dividends declared			(4,331)		(4,331)
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
Balance (in shares) at Dec. 31, 2018	25,422,740
Balance at Dec. 31, 2018	$ 2,542	145,163	249,922	(9,440)	388,187
Net income			10,841		10,841
Other comprehensive income (loss)				4,862	4,862
Repurchase of common stock (in shares)	(674,800)
Repurchase of common stock	$ (67)	(15,264)			(15,331)
Shares withheld upon the vesting and conversion of RSUs (in shares)	(39,947)
Shares withheld upon the vesting and conversion of RSUs	$ (4)	(826)			(830)
Common stock issued under stock compensation plans (in shares)	122,456
Common stock issued under stock compensation plans	$ 12	223			235
Common stock issued under dividend reinvestment and stock purchase plan (in shares)	69,898
Common stock issued under dividend reinvestment and stock purchase plan	$ 7	1,427			1,434
Stock-based compensation		1,295			1,295
Cash dividends declared			(4,251)		(4,251)
Balance (in shares) at Mar. 31, 2019	24,900,347
Balance at Mar. 31, 2019	$ 2,490	132,018	256,512	(4,578)	386,442
Balance (in shares) at Dec. 31, 2018	25,422,740
Balance at Dec. 31, 2018	$ 2,542	145,163	249,922	(9,440)	388,187
Net income					32,368
Other comprehensive income (loss)				8,645	8,645
Balance (in shares) at Sep. 30, 2019	24,182,479
Balance at Sep. 30, 2019	$ 2,418	117,008	269,498	(795)	388,129
Balance (in shares) at Mar. 31, 2019	24,900,347
Balance at Mar. 31, 2019	$ 2,490	132,018	256,512	(4,578)	386,442
Net income			10,744		10,744
Other comprehensive income (loss)				3,320	3,320
Repurchase of common stock (in shares)	(240,300)
Repurchase of common stock	$ (24)	(5,259)			(5,283)
Common stock issued under stock compensation plans (in shares)	1,362
Common stock issued under stock compensation plans		30			30
Stock-based compensation		373			373
Cash dividends declared			(4,189)		(4,189)
Balance (in shares) at Jun. 30, 2019	24,661,409
Balance at Jun. 30, 2019	$ 2,466	127,162	263,067	(1,258)	391,437
Net income			10,783		10,783
Other comprehensive income (loss)				463	463
Repurchase of common stock (in shares)	(494,800)
Repurchase of common stock	$ (50)	(10,825)			(10,875)
Common stock issued under stock compensation plans (in shares)	6,679
Common stock issued under stock compensation plans	$ 1	86			87
Common stock issued under dividend reinvestment and stock purchase plan (in shares)	9,191
Common stock issued under dividend reinvestment and stock purchase plan	$ 1	189			190
Stock-based compensation		396			396
Cash dividends declared			(4,352)		(4,352)
Balance (in shares) at Sep. 30, 2019	24,182,479
Balance at Sep. 30, 2019	$ 2,418	$ 117,008	$ 269,498	$ (795)	$ 388,129