Revenue, Contract Balances (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Revenue [Abstract]
Revenue recognized	$ 700	$ 300
Contract liabilities [Abstract]
Customer pre-payments	72		$ 232
Deferred revenue, current	519		700
Deferred revenue, non-current	145		219
Total contract liabilities	$ 736		$ 1,151