Property and Equipment - Additional Information (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2018 USD ($) Station	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Property, Plant and Equipment [Line Items]
Depreciation expense	$ 10.1	$ 10.5	$ 11.8
FCC
Property, Plant and Equipment [Line Items]
Number of stations assigned to new channels | Station	16
Estimated reimbursable cost	$ 9.8
Total costs incurred and reimbursed	1.2	0.3
Gains on involuntary conversion associated with repack process	$ 1.2	$ 0.3