Intangible Assets - Schedule of Intangible Assets, Other than Goodwill (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Dec. 31, 2020
Intangible Assets Net Excluding Goodwill [Line Items]
Amortized intangible assets, Gross Carrying Amount	$ 66,662	$ 66,334
Amortized intangible assets, Accumulated Amortization	(48,437)	(46,544)
Amortized intangible assets, Net Carrying Amount	18,225	19,790
Total intangible assets, Gross Carrying amount	98,945	98,617
Total intangible assets, Net Carrying Amount	50,508	52,073
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 3 months 18 days
Amortized intangible assets, Gross Carrying Amount	$ 50,357	50,029
Amortized intangible assets, Accumulated Amortization	(33,632)	(31,739)
Amortized intangible assets, Net Carrying Amount	$ 16,725	18,290
Other Intangible Assets [Member]
Intangible Assets Net Excluding Goodwill [Line Items]
Weighted Average Remaining Useful Life (in years)	8 years
Amortized intangible assets, Gross Carrying Amount	$ 1,500	1,500
Amortized intangible assets, Net Carrying Amount	1,500	1,500
Service Customer Relationships [Member]
Intangible Assets Net Excluding Goodwill [Line Items]
Amortized intangible assets, Gross Carrying Amount	8,081	8,081
Amortized intangible assets, Accumulated Amortization	(8,081)	(8,081)
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)