Revenue, Deferred Revenue And Prepaid Commissions - Additional Information and Disaggregation of Revenue (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019 USD ($)	Jun. 30, 2018 USD ($)	Jun. 30, 2019 USD ($) revenue_component	Jun. 30, 2018 USD ($)
Revenues from External Customers and Long-Lived Assets
Total revenue	$ 39,525	$ 40,628	$ 81,288	$ 83,742
Deferred revenue recognized from previous period			24,200
United States
Revenues from External Customers and Long-Lived Assets
Total revenue	38,447	39,109	78,213	81,044
International
Revenues from External Customers and Long-Lived Assets
Total revenue	1,078	1,519	3,075	2,698
Wireless products and services
Revenues from External Customers and Long-Lived Assets
Total revenue	22,127	23,658	44,737	47,927
License
Revenues from External Customers and Long-Lived Assets
Total revenue	1,676	1,993	4,516	6,369
Services
Revenues from External Customers and Long-Lived Assets
Total revenue	4,835	4,363	10,040	8,433
Hardware
Revenues from External Customers and Long-Lived Assets
Total revenue	842	1,107	$ 1,805	2,132
Maintenance
Revenues from External Customers and Long-Lived Assets
Typical duration of revenue recognition			Maintenance revenue is for ongoing support of our software solutions or related equipment (typically for one year).
Total revenue	$ 10,045	$ 9,507	$ 20,190	$ 18,881
Wireless
Revenues from External Customers and Long-Lived Assets
Revenue primary component | revenue_component			2
Software
Revenues from External Customers and Long-Lived Assets
Revenue primary component | revenue_component			2