Income Taxes - Schedule of Components of the Provision for Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Current:
State	$ 4	$ 0	$ 0
Foreign	34	7	6
Total current tax expense	38	7	6
Provision for income taxes	$ 38	$ 7	$ 6