Stockholders' Equity - Summary of common shareholders' equity (Details) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance	$ 31,541	$ 31,513	$ 28,379	$ 28,165	$ 31,513	$ 28,165
Balance (shares)		2,614,506			2,614,506
Dividends declared ($0.16 per share)	(413)		(416)
Purchase of treasury shares	21	$ (128)	(33)	(117)
Stock based compensation	95	58	85
Net Income	714	98	707	331	$ 812	1,038
Balance	$ 31,916	31,541	28,722	28,379	$ 31,916	28,722
Balance (shares)	2,614,506				2,614,506
Common Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance	$ 523	523	523	523	$ 523	523
Dividends declared ($0.16 per share)	0		0
Purchase of treasury shares	0	0	0	0
Stock based compensation	0	0	0
Net Income	0	0	0	0
Balance	523	523	523	523	523	523
Capital in excess of par value
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance	14,264	14,250	14,171	14,171	14,250	14,171
Dividends declared ($0.16 per share)	0		0
Purchase of treasury shares	0	0	0	0
Stock based compensation	34	14	21
Net Income	0	0	0	0
Balance	14,298	14,264	14,192	14,171	14,298	14,192
Retained earnings
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance	18,886	18,788	16,040	15,709	18,788	15,709
Dividends declared ($0.16 per share)	(413)		(416)
Purchase of treasury shares	0	0	0	0
Stock based compensation	0	0	(6)
Net Income	714	98	707	331
Balance	19,187	18,886	16,325	16,040	19,187	16,325
ESOT
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance	(561)	(561)	(662)	(662)	(561)	(662)
Dividends declared ($0.16 per share)	0		0
Purchase of treasury shares	0	0	0	0
Stock based compensation	0	0	0
Net Income	0	0	0	0
Balance	(561)	(561)	(662)	(662)	(561)	(662)
Treasury stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance	(1,606)	(1,522)	(1,661)	(1,544)	(1,522)	(1,544)
Dividends declared ($0.16 per share)	0		0
Purchase of treasury shares	21	(128)	(33)	(117)
Stock based compensation	61	44	64
Net Income	0	0	0	0
Balance	(1,566)	(1,606)	(1,630)	(1,661)	(1,566)	(1,630)
Accumulated Other Comprehensive Income (Loss)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance	35	35	(32)	(32)	35	(32)
Dividends declared ($0.16 per share)	0		0
Purchase of treasury shares	0	0	0	0
Stock based compensation	0	0	6
Net Income	0	0	0	0
Balance	$ 35	$ 35	$ (26)	$ (32)	$ 35	$ (26)