Revenue Recognition - Schedule of Disaggregated Revenue By Major Product Line in Single Reporting Segment (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Disaggregation Of Revenue [Line Items]
Total	$ 6,417	$ 5,751	$ 19,395	$ 18,437
Service [Member]
Disaggregation Of Revenue [Line Items]
Total	3,932	3,352	11,507	10,982
Subscription [Member]
Disaggregation Of Revenue [Line Items]
Total	2,485	2,399	7,888	7,455
Government [Member]
Disaggregation Of Revenue [Line Items]
Total	3,579	3,470	11,286	11,435
Government [Member] | Service [Member]
Disaggregation Of Revenue [Line Items]
Total	3,279	3,170	10,386	10,535
Government [Member] | Subscription [Member]
Disaggregation Of Revenue [Line Items]
Total	300	300	900	900
Commercial [Member]
Disaggregation Of Revenue [Line Items]
Total	2,838	2,281	8,109	7,002
Commercial [Member] | Service [Member]
Disaggregation Of Revenue [Line Items]
Total	653	182	1,121	447
Commercial [Member] | Subscription [Member]
Disaggregation Of Revenue [Line Items]
Total	$ 2,185	$ 2,099	$ 6,988	$ 6,555