Accounts Receivable (Allowance) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Allowance for doubtful accounts:
Balance, beginning of period	$ 119	$ 90	$ 115
Provisions for losses on accounts receivable, net of adjustments	174	179	(25)
Accounts receivable written off, net of recoveries	(29)	(150)	0
Balance, end of period	$ 264	$ 119	$ 90