Revenue, Deferred Revenue And Prepaid Commissions - Additional Information and Disaggregation of Revenue (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2019 USD ($) revenue_component	Mar. 31, 2018 USD ($)
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	$ 41,764	$ 43,114
Deferred revenue recognized from previous period	15,800
Wireless products and services
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	22,610	24,269
License
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	2,840	4,376
Services
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	5,206	4,071
Hardware
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	$ 963	1,024
Maintenance
Revenues from External Customers and Long-Lived Assets [Line Items]
Typical duration of revenue recognition	Maintenance revenue is for ongoing support of our software solutions or related equipment (typically for one year).
Total revenue	$ 10,145	9,374
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	39,766	41,935
International
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	$ 1,998	$ 1,179
Wireless
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue primary component | revenue_component	2
Software
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue primary component | revenue_component	2