Segment, Customer Concentration and Geographical Information - Company Revenue in Different Geographic Locations (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018
Revenue from External Customer [Line Items]
Total revenues	$ 12,278	$ 11,782	$ 10,854	$ 8,432	$ 7,352	$ 6,525	$ 6,945	$ 5,463	$ 43,346	$ 26,285
Americas [Member] | Reportable Geographical Components [Member]
Revenue from External Customer [Line Items]
Total revenues									43,236	26,054
EMEA [Member] | Reportable Geographical Components [Member]
Revenue from External Customer [Line Items]
Total revenues									67	90
Asia Pacific [Member] | Reportable Geographical Components [Member]
Revenue from External Customer [Line Items]
Total revenues									$ 43	$ 141