Fair Value Measurements - Fair Value of Assets and Liabilities Measured on Recurring and Nonrecurring Basis (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Fair Value, Measurements, Recurring | Contingent Consideration
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair Value and Carrying Value on Liabilities	$ 114.9
Fair Value, Measurements, Recurring | Money Market Account
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair Value and Carrying Value on Assets	88.3	$ 59.9
Fair Value, Measurements, Recurring | Certificates of Deposit
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair Value and Carrying Value on Assets		2.8
Fair Value, Measurements, Recurring | Corporate Bonds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair Value and Carrying Value on Assets		25.2
Fair Value, Measurements, Recurring | Level 1 | Money Market Account
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair Value and Carrying Value on Assets	88.3	59.9
Fair Value, Measurements, Recurring | Level 2 | Certificates of Deposit
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair Value and Carrying Value on Assets		2.8
Fair Value, Measurements, Recurring | Level 2 | Corporate Bonds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair Value and Carrying Value on Assets		25.2
Fair Value, Measurements, Recurring | Level 3 | Contingent Consideration
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair Value and Carrying Value on Liabilities	114.9
Fair Value, Measurements, Nonrecurring | Goodwill
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair Value and Carrying Value on Assets		5.2
Total Gains (Losses)		(0.8)
Fair Value, Measurements, Nonrecurring | FCC Licenses
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair Value and Carrying Value on Assets	0.7	101.7
Total Gains (Losses)	(0.1)	(32.5)
Fair Value, Measurements, Nonrecurring | Level 3 | Goodwill
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair Value and Carrying Value on Assets		5.2
Fair Value, Measurements, Nonrecurring | Level 3 | FCC Licenses
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair Value and Carrying Value on Assets	$ 0.7	$ 101.7