Balance Sheet Details - Schedule of Inventory and Other Deferred Costs (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Inventory And Other Deferred Costs [Abstract]
Raw materials	$ 1,969	$ 2,134
Other deferred costs	2,635	1,298
Total inventory and other deferred costs	$ 4,604	$ 3,432