Segment, Customer Concentration and Geographical Information - Wireless Revenues by Product (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Revenue from External Customer [Line Items]
Total revenues	$ 11,381	$ 13,322
Wireless [Member]
Revenue from External Customer [Line Items]
Total revenues	11,381	13,215
Wireless [Member] | SafePath [Member]
Revenue from External Customer [Line Items]
Total revenues	6,267	7,848
Wireless [Member] | CommSuite [Member]
Revenue from External Customer [Line Items]
Total revenues	4,128	4,539
Wireless [Member] | ViewSpot [Member]
Revenue from External Customer [Line Items]
Total revenues	930	745
Wireless [Member] | Other [Member]
Revenue from External Customer [Line Items]
Total revenues	$ 56	$ 83