Summary of Significant Accounting Policies - Summary of Revenue from External Customers by Geographic Areas (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Summary Of Significant Accounting Policies [Line Items]
Total Revenue	$ 1,134	$ 734	$ 2,717	$ 1,521
United States
Summary Of Significant Accounting Policies [Line Items]
Total Revenue	559	221	1,328	456
Europe [Member]
Summary Of Significant Accounting Policies [Line Items]
Total Revenue	$ 575	$ 513	$ 1,389	$ 1,065