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Canadian ATG Spectrum License - Additional Information (Detail) - License Agreement [Member] - Canadian ATG Spectrum License Agreement [Member] - USD ($)
3 Months Ended 9 Months Ended
Sep. 30, 2017
Sep. 30, 2016
Sep. 30, 2017
Sep. 30, 2016
Agreements [Line Items]        
Total amount of monthly payments incurred $ 300,000 $ 300,000 $ 900,000 $ 900,000
Maximum [Member]        
Agreements [Line Items]        
Total amortization expenses $ 100,000 $ 100,000 $ 100,000 $ 100,000