Shareholders' Equity - Summary of common shareholders' equity (Details) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2022	Mar. 31, 2022	Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2022	Jun. 30, 2021
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	$ 35,738	$ 35,366	$ 34,243	$ 33,737	$ 35,366	$ 33,737
Retirement benefits adjustment	22	22	16	15
Stock based compensation	42	25	25	31
Purchase of treasury shares				(81)
Net (loss)/income	(810)	325	1,186	541	(485)	1,727
Ending balance	34,992	35,738	35,470	34,243	34,992	35,470
Retained Earnings
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	26,183	25,858	22,344	21,803	25,858	21,803
Retirement benefits adjustment	0	0	0	0
Stock based compensation	0	0	0	0
Purchase of treasury shares				0
Net (loss)/income	(810)	325	1,186	541
Ending balance	25,373	26,183	23,530	22,344	25,373	23,530
Accumulated Other Comprehensive Income
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	(3,886)	(3,908)	(1,341)	(1,356)	(3,908)	(1,356)
Retirement benefits adjustment	22	22	16	15
Stock based compensation	0	0	0	0
Purchase of treasury shares				0
Net (loss)/income	0	0	0	0
Ending balance	(3,864)	(3,886)	(1,325)	(1,341)	(3,864)	(1,325)
Common Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	523	523	523	523	523	523
Retirement benefits adjustment	0	0	0	0
Stock based compensation	0	0	0	0
Purchase of treasury shares				0
Net (loss)/income	0	0	0	0
Ending balance	523	523	523	523	523	523
Capital in excess of par value
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	14,502	14,500	14,492	14,481	14,500	14,481
Retirement benefits adjustment	0	0	0	0
Stock based compensation	7	2	5	11
Purchase of treasury shares				0
Net (loss)/income	0	0	0	0
Ending balance	14,509	14,502	14,497	14,492	14,509	14,497
ESOT
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	(258)	(258)	(359)	(359)	(258)	(359)
Retirement benefits adjustment	0	0	0	0
Stock based compensation	0	0	0	0
Purchase of treasury shares				0
Net (loss)/income	0	0	0	0
Ending balance	(258)	(258)	(359)	(359)	(258)	(359)
Treasury stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	(1,326)	(1,349)	(1,416)	(1,355)	(1,349)	(1,355)
Retirement benefits adjustment	0	0	0	0
Stock based compensation	35	23	20	20
Purchase of treasury shares				(81)
Net (loss)/income	0	0	0	0
Ending balance	$ (1,291)	$ (1,326)	$ (1,396)	$ (1,416)	$ (1,291)	$ (1,396)