Accounts Receivable - Allowance (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance, beginning of period	$ 392	$ 208	$ 264	$ 119
Provisions for losses on accounts receivables, net of adjustments	(37)	(31)	91	67
Accounts receivable written off, net of recoveries	(2)	0	(2)	(9)
Balance, end of period	$ 353	$ 177	$ 353	$ 177