Geographic Information and Concentrations of Risk - Schedule of Geographic Concentration of Net Revenues (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
Revenues from External Customers and Long-Lived Assets [Line Items]
Net revenues	$ 52,333	$ 62,716	$ 55,891	$ 48,556	$ 56,043	$ 50,630	$ 49,057	$ 46,733	$ 219,496	$ 202,463
United States and Canada
Revenues from External Customers and Long-Lived Assets [Line Items]
Net revenues									158,756	139,246
South Africa
Revenues from External Customers and Long-Lived Assets [Line Items]
Net revenues									35,001	38,608
Other
Revenues from External Customers and Long-Lived Assets [Line Items]
Net revenues									$ 25,739	$ 24,609