Revenue, Contract Balances (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Dec. 31, 2018
Revenue [Abstract]
Revenue recognized	$ 489
Contract liabilities [Abstract]
Customer pre-payments	69	$ 50
Deferred revenue, current	517	384
Deferred revenue, non-current	190	265
Total contract liabilities	$ 776	$ 699