Commitments and Contingencies - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($) ft²	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Contingencies And Commitments [Line Items]
Lease commitment with media research and rating providers, aggregate amount			$ 17,500,000
Non-cancelable operating lease expiration term			2021-01
Total rent expense under operating leases			$ 10,500,000	$ 11,000,000	$ 10,900,000
Santa Monica
Contingencies And Commitments [Line Items]
Area under operating leases for corporate headquarters | ft²			16,000
Lease Expiration Year			2021
Los Angeles
Contingencies And Commitments [Line Items]
Area under operating leases for corporate headquarters | ft²			41,000
Lease Expiration Year			2026
Facilities and Broadcast Equipment
Contingencies And Commitments [Line Items]
Non-cancelable operating lease expiration term			2059-12
Scenario, Forecast
Contingencies And Commitments [Line Items]
Lease commitment with media research and rating providers, annual commitment	$ 5,300,000	$ 11,800,000