Consolidated Statements of Changes in Shareholders' Equity - USD ($) $ in Thousands	Capital Stock [Member]	Retained earnings [Member]	Accumulated other comprehensive income (loss) [Member]	Total
Balance at Dec. 31, 2016	$ 27,155	$ 52,095	$ 1,381	$ 80,631
Balance, shares at Dec. 31, 2016	2,453,805
Net income		6,389		6,389
Other comprehensive income (loss)			540	540
Issuance of common stock through Employee Stock Purchase Plan	$ 126			126
Issuance of common stock through Employee Stock Purchase Plan, shares	4,085
Issuance of common stock through Dividend Reinvestment Plan	$ 331			331
Issuance of common stock through Dividend Reinvestment Plan, shares	7,744
Issuance of common stock from vested restricted share grants through stock compensation plans, shares	9,657
Issuance of common stock through exercise of stock options	$ 332			332
Issuance of common stock through exercise of stock options, shares	11,500
Stock-based compensation expense	$ 256			256
Issuance of common stock from stock split	1,243,187
Cash in lieu of fractional shares paid due to the stock split		(11)		(11)
Cash dividends declared		(2,310)		(2,310)
Balance, shares at Sep. 30, 2017	3,729,978
Balance at Sep. 30, 2017	$ 28,200	56,163	1,921	86,284
Balance at Jun. 30, 2017	$ 27,565	54,719	1,852	84,136
Balance, shares at Jun. 30, 2017	2,470,544
Net income		2,226		2,226
Other comprehensive income (loss)			69	69
Issuance of common stock through Dividend Reinvestment Plan	$ 241			241
Issuance of common stock through Dividend Reinvestment Plan, shares	5,266
Issuance of common stock through exercise of stock options	$ 317			317
Issuance of common stock through exercise of stock options, shares	10,981
Stock-based compensation expense	$ 77			77
Issuance of common stock from stock split	1,243,187
Cash in lieu of fractional shares paid due to the stock split		(11)		(11)
Cash dividends declared		(771)		(771)
Balance, shares at Sep. 30, 2017	3,729,978
Balance at Sep. 30, 2017	$ 28,200	56,163	1,921	86,284
Balance at Dec. 31, 2017	$ 28,361	57,218	1,804	87,383
Balance, shares at Dec. 31, 2017	3,734,478
Net income		8,159		8,159
Other comprehensive income (loss)			(3,926)	(3,926)
Effect of adopting ASU 2016-01		421	(421)
Issuance of common stock through Employee Stock Purchase Plan	$ 149			149
Issuance of common stock through Employee Stock Purchase Plan, shares	6,783
Issuance of common stock through Dividend Reinvestment Plan	$ 311			311
Issuance of common stock through Dividend Reinvestment Plan, shares	5,486
Issuance of common stock from vested restricted share grants through stock compensation plans, shares	9,994
Issuance of common stock through exercise of stock options	$ 14			14
Issuance of common stock through exercise of stock options, shares	750
Stock-based compensation expense	$ 685			685
Cash dividends declared		(2,723)		(2,723)
Balance, shares at Sep. 30, 2018	3,757,491
Balance at Sep. 30, 2018	$ 29,520	63,075	(2,543)	90,052
Balance at Jun. 30, 2018	$ 29,016	61,119	(1,283)	88,852
Balance, shares at Jun. 30, 2018	3,752,005
Net income		2,863		2,863
Other comprehensive income (loss)			(1,260)	(1,260)
Issuance of common stock through Dividend Reinvestment Plan	$ 311			311
Issuance of common stock through Dividend Reinvestment Plan, shares	5,486
Stock-based compensation expense	$ 193			193
Cash dividends declared		(907)		(907)
Balance, shares at Sep. 30, 2018	3,757,491
Balance at Sep. 30, 2018	$ 29,520	$ 63,075	$ (2,543)	$ 90,052