Fair Value of Financial Assets and Liabilities - Additional Information (Detail) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Contingent consideration, Fair Value	$ 41,026	$ 45,984
Level 3 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Contingent consideration, Fair Value	41,000	46,000
Undiscounted value of the payments on all contingencies	58,900	66,100
Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Alternative to equity securities	$ 24,400	$ 55,800