Significant Transactions - Additional Information (Detail) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017 USD ($)	Jun. 30, 2017 USD ($)	Sep. 30, 2017 USD ($) Station
Significant Transactions [Line Items]
Revenue from spectrum usage rights	$ 263,943		$ 263,943
Cost of revenue - television (spectrum usage rights)	12,131		12,131
Payment for relocation of television station		$ 32,600
FCC
Significant Transactions [Line Items]
Revenue from spectrum usage rights	263,900		263,900
Cost of revenue - television (spectrum usage rights)	$ 12,100		$ 12,100
Television | FCC
Significant Transactions [Line Items]
Number of stations owned from spectrum usage rights | Station			4