Revenue, Deferred Revenue And Prepaid Commissions - Additional Information and Disaggregation of Revenue (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019 USD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2019 USD ($) revenue_component	Sep. 30, 2018 USD ($)
Revenues from External Customers and Long-Lived Assets
Total revenue	$ 39,453	$ 42,476	$ 120,741	$ 126,218
Deferred revenue recognized from previous period			28,500
United States
Revenues from External Customers and Long-Lived Assets
Total revenue	38,312	41,198	116,525	122,243
International
Revenues from External Customers and Long-Lived Assets
Total revenue	1,141	1,278	4,216	3,975
Wireless products and services
Revenues from External Customers and Long-Lived Assets
Total revenue	21,814	23,259	66,552	71,186
License
Revenues from External Customers and Long-Lived Assets
Total revenue	2,723	3,175	7,239	9,544
Services
Revenues from External Customers and Long-Lived Assets
Total revenue	4,202	4,555	14,242	12,988
Hardware
Revenues from External Customers and Long-Lived Assets
Total revenue	689	1,296	$ 2,493	3,428
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	$ 10,025	$ 10,191	$ 30,215	$ 29,072
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