Accounts Receivable (Allowance) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Allowance for Doubtful Accounts Receivable [Roll Forward]
Balance, beginning of period	$ 81	$ 73	$ 90	$ 115
Provisions for losses on accounts receivables, net of recoveries	(39)	(72)	(180)	(30)
Accounts receivable written off, net of recoveries	0	0	(150)	0
Balance, end of period	$ 120	$ 145	$ 120	$ 145