Stockholders' Equity - Summary of common shareholders' equity (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance	$ 31,513	$ 28,165
Balance (shares)	2,614,506
Net income	$ 98	331
Purchase of treasury shares	(128)	(117)
Stock based compensation, net of tax benefit	58
Balance	$ 31,541	28,379
Balance (shares)	2,614,506
Common Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance	$ 523	$ 523
Balance (shares)	2,614,506	2,614,506
Net income	$ 0	$ 0
Purchase of treasury shares	0	0
Stock based compensation, net of tax benefit	0
Balance	$ 523	$ 523
Balance (shares)	2,614,506	2,614,506
Capital in excess of par value
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance	$ 14,250	$ 14,171
Net income	0	0
Purchase of treasury shares	0	0
Stock based compensation, net of tax benefit	14
Balance	14,264	14,171
Retained earnings
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance	18,788	15,709
Net income	98	331
Purchase of treasury shares	0	0
Stock based compensation, net of tax benefit	0
Balance	18,886	16,040
ESOT
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance	(561)	(662)
Net income	0	0
Purchase of treasury shares	0	0
Stock based compensation, net of tax benefit	0
Balance	(561)	(662)
Treasury stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance	(1,522)	(1,544)
Net income	0	0
Purchase of treasury shares	(128)	(117)
Stock based compensation, net of tax benefit	44
Balance	(1,606)	(1,661)
Accumulated Other Comprehensive Income (Loss)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance	35	(32)
Net income	0	0
Purchase of treasury shares	0	0
Stock based compensation, net of tax benefit	0
Balance	$ 35	$ (32)