Consolidated Statements Of Changes In Shareholders' Equity - USD ($) $ in Thousands	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Loss [Member]	Treasury Stock [Member]	Total
Balance at Dec. 31, 2016	$ 4,688	$ 39,752	$ 83,081	$ (4,215)	$ (6,813)	$ 116,493
Net income			9,439			9,439
Other comprehensive income (loss)				608		608
Cash dividends declared			(2,988)			(2,988)
Treasury shares issued under employee stock purchase plan		29			120	149
Treasury shares issued under dividend reinvestment plan		296			422	718
Stock option compensation expense		161				161
Balance at Sep. 30, 2017	4,688	40,238	89,532	(3,607)	(6,271)	124,580
Balance at Jun. 30, 2017	4,688	40,096	87,498	(3,542)	(6,380)	122,360
Net income			3,076			3,076
Other comprehensive income (loss)				(65)		(65)
Cash dividends declared			(1,042)			(1,042)
Treasury shares issued under employee stock purchase plan		3			4	7
Treasury shares issued under dividend reinvestment plan		85			105	190
Stock option compensation expense		54				54
Balance at Sep. 30, 2017	4,688	40,238	89,532	(3,607)	(6,271)	124,580
Balance at Dec. 31, 2017	4,689	40,396	82,218	(6,028)	(6,131)	115,144
Cumulative adjustment for fair value of equity securities			201	(201)
Net income			2,321			2,321
Other comprehensive income (loss)				(1,561)		(1,561)
Cash dividends declared			(3,410)			(3,410)
Acquisition of 2,605 shares of treasury stock					(88)	(88)
Treasury shares issued under employee stock purchase plan		34			54	88
Treasury shares issued under dividend reinvestment plan		513			572	1,085
Common stock issued under incentive stock option plan	12	252				264
Stock option compensation expense		185				185
Balance at Sep. 30, 2018	4,701	41,380	81,330	(7,790)	(5,593)	114,028
Balance at Jun. 30, 2018	4,700	41,079	78,514	(7,282)	(5,839)	111,172
Net income			4,000			4,000
Other comprehensive income (loss)				(508)		(508)
Cash dividends declared			(1,184)			(1,184)
Treasury shares issued under employee stock purchase plan		5			7	12
Treasury shares issued under dividend reinvestment plan		210			239	449
Common stock issued under incentive stock option plan	1	24				25
Stock option compensation expense		62				62
Balance at Sep. 30, 2018	$ 4,701	$ 41,380	$ 81,330	$ (7,790)	$ (5,593)	$ 114,028