Income Taxes - Significant Components of Deferred Tax Assets (Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Deferred Tax Assets:
Net operating loss carryforwards	$ 6,990	$ 1,994
Other accruals	88	79
Reserves	203	142
Deferred revenue	661	697
Intangible assets	353	618
Stock-based compensation	6,464	4,314
Deferred tax assets gross	14,759	7,844
Deferred Tax Liabilities:
Property and equipment	(888)	(5)
Valuation allowance	$ (13,871)	$ (7,839)