Intangible Assets - Schedule of Intangible Assets, Other than Goodwill (Detail) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Dec. 31, 2017
Intangible Assets Net Excluding Goodwill [Line Items]
Total intangible assets, Gross Carrying Amount	$ 202,472	$ 193,651
Amortized intangible assets, Gross Carrying Amount	170,189	161,368
Amortized intangible assets, Accumulated Amortization	(120,014)	(107,138)
Amortized intangible assets, Net Carrying Amount	50,175	54,230
Total intangible assets, Net Carrying Amount	82,458	86,513
FCC Licenses [Member]
Intangible Assets Net Excluding Goodwill [Line Items]
Total unamortized intangible assets, Gross Carrying Amount	32,283	32,283
Total unamortized intangible assets, Net Carrying Amount	$ 32,283	32,283
Software [Member]
Intangible Assets Net Excluding Goodwill [Line Items]
Weighted Average Remaining Useful Life (in years)	2 years 1 month 6 days
Amortized intangible assets, Gross Carrying Amount	$ 153,884	145,063
Amortized intangible assets, Accumulated Amortization	(105,701)	(93,523)
Amortized intangible assets, Net Carrying Amount	$ 48,183	51,540
Service Customer Relationships [Member]
Intangible Assets Net Excluding Goodwill [Line Items]
Weighted Average Remaining Useful Life (in years)	1 year 9 months 18 days
Amortized intangible assets, Gross Carrying Amount	$ 8,081	8,081
Amortized intangible assets, Accumulated Amortization	(6,296)	(5,788)
Amortized intangible assets, Net Carrying Amount	$ 1,785	2,293
Other Intangible Assets [Member]
Intangible Assets Net Excluding Goodwill [Line Items]
Weighted Average Remaining Useful Life (in years)	1 year 8 months 12 days
Amortized intangible assets, Gross Carrying Amount	$ 1,500	1,500
Amortized intangible assets, Accumulated Amortization	(1,293)	(1,103)
Amortized intangible assets, Net Carrying Amount	207	397
OEM and Dealer Relationships [Member]
Intangible Assets Net Excluding Goodwill [Line Items]
Amortized intangible assets, Gross Carrying Amount	6,724	6,724
Amortized intangible assets, Accumulated Amortization	$ (6,724)	$ (6,724)