Segment Information - Additional Information (Detail)	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018 Segment Station Market	Sep. 30, 2017
Segment Reporting Information [Line Items]
Number of reportable segments | Segment			3
Percentage of revenue generated from outside the United States	21.00%	3.00%	20.00%	5.00%
U.S.
Segment Reporting Information [Line Items]
Number of markets in radio stations owned | Market			16
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 stations owned			300