Fair Value of Financial Assets and Liabilities - Additional Information (Detail) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Level 3 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Undiscounted value of the payments on all contingencies	$ 62,100	$ 66,100
Accounts Payable, Accrued and Other Liabilities [Member] | Contingent Consideration [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Contingent consideration, Fair Value	42,139	45,984
Accounts Payable, Accrued and Other Liabilities [Member] | Level 3 [Member] | Contingent Consideration [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Contingent consideration, Fair Value	42,100	46,000
Other Assets [Member] | Level 3 [Member] | Non-recurring Basis [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Equity securities, Assets	$ 24,400	$ 55,800