Shareholders' Equity - Summary of common shareholders' equity (Details) - USD ($)	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Shareholders' Equity
Beginning balance	$ 35,112,000	$ 35,366,000
Retirement benefits adjustment	13,000	22,000
Stock based compensation	41,000	25,000
Net (Loss)Income	(1,547,000)	325,000
Ending balance	33,619,000	35,738,000
Retained earnings
Shareholders' Equity
Beginning balance	23,741,000	25,858,000
Retirement benefits adjustment	0	0
Stock based compensation	0	0
Net (Loss)Income	(1,547,000)	325,000
Ending balance	22,194,000	26,183,000
Accumulated Other Comprehensive Loss
Shareholders' Equity
Beginning balance	(2,337,000)	(3,908,000)
Retirement benefits adjustment	13,000	22,000
Stock based compensation	0	0
Net (Loss)Income	0	0
Ending balance	(2,324,000)	(3,886,000)
Common Stock
Shareholders' Equity
Beginning balance	523,000	523,000
Retirement benefits adjustment	0	0
Stock based compensation	0	0
Net (Loss)Income	0	0
Ending balance	523,000	523,000
Capital in excess of par value
Shareholders' Equity
Beginning balance	14,556,000	14,500,000
Retirement benefits adjustment	0	0
Stock based compensation	17,000	2,000
Net (Loss)Income	0	0
Ending balance	14,573,000	14,502,000
ESOT
Shareholders' Equity
Beginning balance	(157,000)	(258,000)
Retirement benefits adjustment	0	0
Stock based compensation	0	0
Net (Loss)Income	0	0
Ending balance	(157,000)	(258,000)
Treasury stock
Shareholders' Equity
Beginning balance	(1,214,000)	(1,349,000)
Retirement benefits adjustment	0	0
Stock based compensation	24,000	23,000
Net (Loss)Income	0	0
Ending balance	$ (1,190,000)	$ (1,326,000)