Commitments and Contingencies - Additional Information (Detail) $ in Thousands	1 Months Ended		3 Months Ended		12 Months Ended
	Aug. 31, 2017 USD ($) ft²	May 31, 2017	Mar. 31, 2018 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Commitments And Contingencies Disclosure [Line Items]
Rent expense under leases			$ 200	$ 200
Refund liability related to estimated sales returns			200		$ 200
Warranty reserve			$ 378		382
Antenna [Member]
Commitments And Contingencies Disclosure [Line Items]
Repair and replacement warranty			5 years
Warranty Reserves [Member]
Commitments And Contingencies Disclosure [Line Items]
Warranty reserve			$ 378	$ 420	$ 382	$ 394
Akron, Ohio [Member]
Commitments And Contingencies Disclosure [Line Items]
Annual capital lease obligation	$ 100
Capital lease, assumed occupancy date	2018-03
Akron, Ohio [Member] | Connected Solutions [Member]
Commitments And Contingencies Disclosure [Line Items]
Lease term	7 years
Area of office space | ft²	5,977
Colorado Office [Member]
Commitments And Contingencies Disclosure [Line Items]
Lease expiration date		Oct. 31, 2020