Receivables (Narrative) (Details)	9 Months Ended
	Sep. 30, 2017 USD ($) payment	Dec. 31, 2016 USD ($)
Receivables [Abstract]
Allowance for doubtful accounts receivable	$ 6,559,000	$ 6,916,000
Number of missed payments before delinquent | payment	3
Typical financing period	12 months
Credit amount requiring additional analysis	$ 250,000
Average period of adjudication	18 months
Installment receivable purchased from DLL	$ 2,152,000