Receivables - Installment Receivables (Details) - USD ($)	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Receivables [Abstract]
Installment receivables, current	$ 1,192,000	$ 1,986,000
Installment receivables, long-term	1,257,000	1,374,000
Total Installment Receivables	2,449,000	3,360,000
Unearned Interest - Current	22,000	22,000
Unearned interest, long-term	0	0
Total Unearned Interest	3,173,000	2,416,000
Unearned Interest	22,000	22,000
Installment receivables net of unearned interest, current	1,170,000	1,964,000
Installment receivables net of unearned interest, long-term	1,257,000	1,374,000
Total installment receivables net of unearned interest	2,427,000	3,338,000
Allowance for doubtful accounts, current	(434,000)	(390,000)
Allowance for doubtful accounts, long-term	(1,080,000)	(1,152,000)
Allowance for doubtful accounts	(1,514,000)	(1,542,000)	$ (2,644,000)
Installment receivables, net	736,000	1,574,000
Installment receivables, long-term	177,000	222,000
Total installment receivables, net	$ 913,000	$ 1,796,000