Nature of Business - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2017 Segment Station Location
Segment Reporting Information [Line Items]
Number of reportable segments | Segment	3
Television
Segment Reporting Information [Line Items]
Number of stations owned	55
Radio
Segment Reporting Information [Line Items]
Number of stations owned	49
Radio operations stations, number of location | Location	16
Advertisements and Syndicate Radio Programming | Minimum
Segment Reporting Information [Line Items]
Number of stations owned	300