Consolidated Statement 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			35,122		35,122
Other comprehensive income (loss)				2,150	2,150
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)	164,720
Common stock issued under stock compensation plans	$ 17	959			976
Common stock issued under dividend reinvestment and stock purchase plan (in shares)	823,902
Common stock issued under dividend reinvestment and stock purchase plan	$ 82	22,516			22,598
Stock-based compensation		2,434			2,434
Cash dividends declared			(14,133)		(14,133)
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			41,573		41,573
Other comprehensive income (loss)				(9,709)	(9,709)
Reclassification of stranded tax effects upon the adoption of ASU 2018-02			277	(277)
Repurchase of common stock (in shares)	(77,300)
Repurchase of common stock	$ (8)	(1,533)			(1,541)
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)	(27,591)
Shares withheld upon the vesting and conversion of RSUs	$ (3)	(771)			(774)
Common stock issued under stock compensation plans (in shares)	174,164
Common stock issued under stock compensation plans	$ 17	727			744
Common stock issued under dividend reinvestment and stock purchase plan (in shares)	699,626
Common stock issued under dividend reinvestment and stock purchase plan	$ 70	18,169			18,239
Stock-based compensation		1,814			1,814
Cash dividends declared			(16,243)		(16,243)
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			41,555		41,555
Other comprehensive income (loss)				10,035	10,035
Repurchase of common stock (in shares)	(1,686,100)
Repurchase of common stock	$ (169)	(38,002)			(38,171)
Shares withheld upon the vesting and conversion of RSUs (in shares)	(41,018)
Shares withheld upon the vesting and conversion of RSUs	$ (4)	(850)			(854)
Common stock issued under stock compensation plans (in shares)	150,988
Common stock issued under stock compensation plans	$ 15	570			585
Common stock issued under dividend reinvestment and stock purchase plan (in shares)	88,022
Common stock issued under dividend reinvestment and stock purchase plan	$ 9	1,813			1,822
Stock-based compensation		3,050			3,050
Cash dividends declared			(17,101)		(17,101)
Balance (in shares) at Dec. 31, 2019	23,934,632
Balance at Dec. 31, 2019	$ 2,393	$ 111,744	$ 274,376	$ 595	$ 389,108