Segment Information - Geographical Segment Revenue (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	$ 5,553	$ 5,751	$ 6,497	$ 6,189	$ 5,319	$ 5,828	$ 6,180	$ 5,660	$ 23,990	$ 22,987
Domestic [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue									7,419	7,187
International [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue									$ 16,571	$ 15,800