Changes in Deferred Revenue (Detail) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Revenue From Contract With Customer [Abstract]
Deferred revenue	$ 2,833	$ 2,810
Fair value of deferred revenue acquired in acquisition, net of recognition		4
Deferral of revenue billed in current period, net of recognition	1,719	2,567
Recognition of revenue deferred in prior periods	(1,877)	(1,816)
Deferred revenue	$ 2,675	$ 3,565