Commitments and Contingencies - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2001
Long Term Purchase Commitment [Line Items]
Lease payment and rent expense	$ 4,020	$ 3,401	$ 3,047
Carrier Data Providers [Member]
Long Term Purchase Commitment [Line Items]
Future minimum payments for the year, 2019	7,607
Future minimum payments for the year, 2020	5,723
Future minimum payments for the year, 2021	5,866
Future minimum payments for the year, 2022	6,012
Vendor Parts Supplier [Member]
Long Term Purchase Commitment [Line Items]
Future minimum payments for the year, 2019	1,058
Procurement Agreement [Member] | Europe [Member] | Airtime [Member]
Long Term Purchase Commitment [Line Items]
Credits provided				$ 3,736
Credits used	30	31	$ 28
Unused credits granted	$ 1,948	$ 1,978