Consolidated Statements of Changes in Stockholders' Equity (unaudited) - USD ($) $ in Thousands	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Loss [Member]	Total
Beginning Balance at Dec. 31, 2016	$ 24,806	$ 16,427	$ 56,965	$ (4,208)	$ 93,990
Beginning Balance (in shares) at Dec. 31, 2016	4,961,258
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	$ 0	0	942	0	942
Other comprehensive income (loss), net of tax	0	0	0	428	428
Exercise of stock options	$ 90	271	0	0	361
Exercise of stock options (in shares)	18,006
Employee Stock Purchase Plan share issuance	$ 4	17	0	0	21
Employee Stock Purchase Plan share issuance (in shares)	773
Repurchase and retirement of common stock	$ (14)	(60)	0	0	(74)
Repurchase and retirement of common stock (in shares)	(2,770)
Cash dividends	$ 0	0	(547)	0	(547)
Ending Balance at Mar. 31, 2017	$ 24,886	16,655	57,360	(3,780)	95,121
Ending Balance (in shares) at Mar. 31, 2017	4,977,267
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Reclassification of the income tax effects of the Tax Cuts and Jobs Act from AOCI | ASU 2018-02 [Member]	$ 0	0	139	(139)	0
Reclassification of net unrealized gains on equity securities from AOCI per ASU 2016-01 | ASU 2016-01 [Member]	0	0	77	(77)	0
Beginning Balance at Dec. 31, 2017	$ 25,087	17,270	54,738	(707)	$ 96,388
Beginning Balance (in shares) at Dec. 31, 2017	5,017,458				5,019,703
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	$ 0	0	942	0	$ 942
Other comprehensive income (loss), net of tax	0	0	0	(1,814)	(1,814)
Employee Stock Purchase Plan share issuance	$ 6	20	0	0	26
Employee Stock Purchase Plan share issuance (in shares)	1,081
Stock-based compensation expense	$ 0	8	0	0	8
Cash dividends	0	0	(552)	0	(552)
Ending Balance at Mar. 31, 2018	$ 25,093	$ 17,298	$ 55,344	$ (2,737)	$ 94,998
Ending Balance (in shares) at Mar. 31, 2018	5,018,539				5,020,784