Segment Data - Additional Information (Detail)		12 Months Ended
	Apr. 04, 2017	Dec. 31, 2018 Segment Station Market	Dec. 31, 2017	Dec. 31, 2016
Segment Reporting Information [Line Items]
Number of reportable segments | Segment		3
Percentage of revenue generated from outside the United States		18.00%	7.00%	0.00%
Headway
Segment Reporting Information [Line Items]
Business acquisition date	Apr. 04, 2017
Television
Segment Reporting Information [Line Items]
Number of stations owned		55
Radio
Segment Reporting Information [Line Items]
Number of stations owned		49
Advertisements and Syndicates Radio Programming | Minimum
Segment Reporting Information [Line Items]
Number of markets owned | Market		100