Shareholders' Equity - Summary of common shareholders' equity (Details) - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2022	Sep. 30, 2021
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	$ 34,992	$ 35,738	$ 35,366	$ 35,470	$ 34,243	$ 33,737	$ 35,366	$ 33,737
Retirement benefits adjustment	22	22	22	15	16	15
Stock based compensation	59	42	25	25	25	31
Purchase of treasury shares						(81)
Net (loss)/income	(316)	(810)	325	3,238	1,186	541	(801)	4,965
Ending balance	34,757	34,992	35,738	38,748	35,470	34,243	34,757	38,748
Retained Earnings
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	25,373	26,183	25,858	23,530	22,344	21,803	25,858	21,803
Retirement benefits adjustment	0	0	0	0	0	0
Stock based compensation	0	0	0	0	0	0
Purchase of treasury shares						0
Net (loss)/income	(316)	(810)	325	3,238	1,186	541
Ending balance	25,057	25,373	26,183	26,768	23,530	22,344	25,057	26,768
Accumulated Other Comprehensive Income
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	(3,864)	(3,886)	(3,908)	(1,325)	(1,341)	(1,356)	(3,908)	(1,356)
Retirement benefits adjustment	22	22	22	15	16	15
Stock based compensation	0	0	0	0	0	0
Purchase of treasury shares						0
Net (loss)/income	0	0	0	0	0	0
Ending balance	(3,842)	(3,864)	(3,886)	(1,310)	(1,325)	(1,341)	(3,842)	(1,310)
Common Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	523	523	523	523	523	523	523	523
Retirement benefits adjustment	0	0	0	0	0	0
Stock based compensation	0	0	0	0	0	0
Purchase of treasury shares						0
Net (loss)/income	0	0	0	0	0	0
Ending balance	523	523	523	523	523	523	523	523
Capital in excess of par value
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	14,509	14,502	14,500	14,497	14,492	14,481	14,500	14,481
Retirement benefits adjustment	0	0	0	0	0	0
Stock based compensation	26	7	2	1	5	11
Purchase of treasury shares						0
Net (loss)/income	0	0	0	0	0	0
Ending balance	14,535	14,509	14,502	14,498	14,497	14,492	14,535	14,498
ESOT
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	(258)	(258)	(258)	(359)	(359)	(359)	(258)	(359)
Retirement benefits adjustment	0	0	0	0	0	0
Stock based compensation	0	0	0	0	0	0
Purchase of treasury shares						0
Net (loss)/income	0	0	0	0	0	0
Ending balance	(258)	(258)	(258)	(359)	(359)	(359)	(258)	(359)
Treasury stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	(1,291)	(1,326)	(1,349)	(1,396)	(1,416)	(1,355)	(1,349)	(1,355)
Retirement benefits adjustment	0	0	0	0	0	0
Stock based compensation	33	35	23	24	20	20
Purchase of treasury shares						(81)
Net (loss)/income	0	0	0	0	0	0
Ending balance	$ (1,258)	$ (1,291)	$ (1,326)	$ (1,372)	$ (1,396)	$ (1,416)	$ (1,258)	$ (1,372)