Commitments and Contingencies - Additional Information (Detail) $ in Thousands			1 Months Ended		3 Months Ended		9 Months Ended		12 Months Ended
	Oct. 10, 2014 USD ($)	Sep. 30, 2014 USD ($)	Oct. 31, 2015 USD ($) ft²	May. 31, 2015 USD ($) ft²	Sep. 30, 2015 USD ($) ft² Employees	Sep. 30, 2014 USD ($)	Sep. 30, 2015 USD ($) ft² Employees	Sep. 30, 2014 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)
Commitments And Contingencies Disclosure [Line Items]
Rent expense under leases					$ 300	$ 200	$ 800	$ 700
Lease expiration date							Oct. 31, 2015
Allowance for sales returns							$ 200		$ 100
Warranty reserve					381		381		304
Restructuring charges					$ 413	0	$ 852	0
Number of employees terminated | Employees					18		20
Severance and Employee Related Costs [Member]
Commitments And Contingencies Disclosure [Line Items]
Restructuring charges					$ 400		$ 400
Disposal of Fixed Assets [Member]
Commitments And Contingencies Disclosure [Line Items]
Restructuring charges							23
Mobile Towers [Member]
Commitments And Contingencies Disclosure [Line Items]
Intangible assets written off related to mobile towers							400
Mobile Towers [Member] | Disposal of Fixed Assets [Member]
Commitments And Contingencies Disclosure [Line Items]
Restructuring charges					$ 23		$ 23
Other Party [Member]
Commitments And Contingencies Disclosure [Line Items]
Acquisition related legal settlements	$ 800
Acquisition Related Costs [Member]
Commitments And Contingencies Disclosure [Line Items]
Acquisition related legal settlements		$ 100
Schaumburg, Illinois [Member]
Commitments And Contingencies Disclosure [Line Items]
Area of office space | ft²					6,652		6,652
Lease expiration date							Oct. 31, 2018
Lease obligations				$ 39	$ 400		$ 400
Englewood, Colorado [Member]
Commitments And Contingencies Disclosure [Line Items]
Area of office space | ft²				4,579
Lease expiration date				Feb. 28, 2021
Lease obligations				$ 600
Lease term				5 years
Tianjin, China [Member] | Subsequent Event [Member]
Commitments And Contingencies Disclosure [Line Items]
Area of office space | ft²			22,163
Lease expiration date			Oct. 31, 2020
Lease obligations			$ 200
Lease term			5 years
Warranty Reserves [Member]
Commitments And Contingencies Disclosure [Line Items]
Warranty reserve		$ 307			$ 381	$ 307	$ 381	$ 307	$ 304	$ 305
Antenna [Member]
Commitments And Contingencies Disclosure [Line Items]
Repair and replacement warranty							5 years