Summary of Intangible Assets (Parenthetical) (Detail) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2018	Dec. 31, 2017
Finite-Lived Intangible Assets [Line Items]
Finite lived intangible assets, gross		$ 8,361	$ 6,161
NB-IoT technologies
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, acquired		2,800
Finite-lived intangible assets, balance not received		600
Finite lived intangible assets, gross	[1]	2,200
Capital expenditures incurred but not yet paid		$ 1,350

[1] During the first quarter of 2018, the Company entered into an agreement to acquire certain NB-IoT technologies to be used in the Company's research and development activities in the amount of $2,800, of which $600 has not been received. Of the $2,200, $1,350 has not resulted in cash outflows as of March 31, 2018.