Fair Value Measurements and Investments- Schedule of Financial Assets and Liabilities Recorded at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Fair Value, Inputs, Level 3 [Member] | Debt Security [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets fair value	$ 0	$ 17,820	$ 16,050	$ 12,220
Fair Value, Measurements, Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets fair value	219	18,529
Contingent consideration	(42,700)	(28,560)
Deferred compensation plan, Liabilities	(1,255)	(1,275)
Liabilities fair value, Total	(43,955)	(29,835)
Fair Value, Measurements, Recurring [Member] | Equity Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets fair value	219	219
Fair Value, Measurements, Recurring [Member] | Treasury Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets fair value		490
Fair Value, Measurements, Recurring [Member] | Debt Security [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets fair value		17,820
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets fair value		490
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Treasury Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets fair value		490
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets fair value	219	219
Deferred compensation plan, Liabilities	(1,255)	(1,275)
Liabilities fair value, Total	(1,255)	(1,275)
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Equity Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets fair value	219	219
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets fair value		17,820
Contingent consideration	(42,700)	(28,560)
Liabilities fair value, Total	$ (42,700)	(28,560)
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Debt Security [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets fair value		$ 17,820