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Fair Value of Financial Assets and Liabilities - Additional Information (Detail) - USD ($) $ in Thousands | Mar. 31, 2019 | Dec. 31, 2018
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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

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