Summary of Significant Accounting Policies - Components of Revenue from Contracts with Customers (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Revenue from contracts with customers:
Total revenue from contracts with customers	$ 60,623	$ 67,707	$ 182,626	$ 197,552
Revenue recognized under ASC 842	1,119	1,486	2,027	4,779
Total revenues	61,742	69,193	184,653	202,331
Recurring Service Revenues [Member]
Revenue from contracts with customers:
Total revenue from contracts with customers	36,393	39,161	113,252	115,196
Other Service Revenues [Member]
Revenue from contracts with customers:
Total revenue from contracts with customers	3,345	1,389	5,439	4,099
Service [Member]
Revenue from contracts with customers:
Total revenue from contracts with customers	39,738	40,550	118,691	119,295
Product [Member]
Revenue from contracts with customers:
Total revenue from contracts with customers	20,885	27,157	63,935	78,257
Total revenues	$ 22,004	$ 28,643	$ 65,962	$ 83,036