Receivables (Installment Recevables) (Details) - USD ($)	Jun. 30, 2019	Dec. 31, 2018	Dec. 31, 2017
Receivables [Abstract]
Non-Impaired Financing Receivable, Related Allowance	$ 0	$ 0
Installment Receivables, Current	1,284,000	1,986,000
Installment Receivables, Long-Term	1,446,000	1,374,000
Total Installment Receivables	2,730,000	3,360,000
Unearned Interest	23,000	22,000
Unearned Interest - Noncurrent	0	0
Total Unearned Interest	(2,676,000)	(2,416,000)
Unearned Interest	23,000	22,000
Installment Receivables Net of Unearned Interest Current	1,261,000	1,964,000
Installment Receivables Net of Unearned Interest Noncurrent	1,446,000	1,374,000
Installment Receivables, Net of Unearned Interest	2,707,000	3,338,000
Allowance for doubtful accounts, current	(638,000)	(390,000)
Allowance for doubtful accounts, long-term	(899,000)	(1,152,000)
Allowance for doubtful accounts	(1,537,000)	(1,542,000)	$ (2,644,000)
Installment receivables, net	623,000	1,574,000
Installment receivables, net, long-term	547,000	222,000
Installment receivables, net	$ 1,170,000	$ 1,796,000