Accounts Receivable (Allowance) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Allowance for Doubtful Accounts Receivable [Roll Forward]
Balance, beginning of period	$ 208	$ 81	$ 119	$ 90
Provisions for losses on accounts receivables, net of recoveries	(31)	39	67	180
Accounts receivable written off	0	0	9	150
Balance, end of period	$ 177	$ 120	$ 177	$ 120