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Schedule of Reported Financial Assets and Liabilities (Detail) - Fair Value, Measurements, Recurring - USD ($) $ in Thousands | Dec. 31, 2020 | Dec. 31, 2019
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Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis |  |
Assets | $ 1,554,476 | $ 1,016,245
Liabilities | 7,731 | 39,908
Other Current Liabilities |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis |  |
Liabilities | 504 | 203
Cash and Cash Equivalents |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis |  |
Assets | 914,121 | 773,924
Marketable securities |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis |  |
Assets | 522,280 | 137,303
Long-term marketable securities |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis |  |
Assets | 117,980 | 104,490
Prepayments and other current assets |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis |  |
Assets | 95 | 528
Contingent Consideration |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis |  |
Liabilities |  | 9,106
Long Term Contingent Consideration |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis |  |
Liabilities | 7,227 | 30,599
Quoted Prices in Active Markets for Identical Instruments (Level 1) |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis |  |
Assets | 828,919 | 754,920
Quoted Prices in Active Markets for Identical Instruments (Level 1) | Cash and Cash Equivalents |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis |  |
Assets | 790,934 | 722,260
Quoted Prices in Active Markets for Identical Instruments (Level 1) | Long-term marketable securities |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis |  |
Assets | 37,985 | 32,660
Significant Other Observable Inputs (Level 2) |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis |  |
Assets | 725,557 | 261,325
Liabilities | 504 | 203
Significant Other Observable Inputs (Level 2) | Other Current Liabilities |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis |  |
Liabilities | 504 | 203
Significant Other Observable Inputs (Level 2) | Cash and Cash Equivalents |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis |  |
Assets | 123,187 | 51,664
Significant Other Observable Inputs (Level 2) | Marketable securities |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis |  |
Assets | 522,280 | 137,303
Significant Other Observable Inputs (Level 2) | Long-term marketable securities |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis |  |
Assets | 79,995 | 71,830
Significant Other Observable Inputs (Level 2) | Prepayments and other current assets |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis |  |
Assets | 95 | 528
Significant Unobservable Inputs (Level 3) |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis |  |
Liabilities | 7,227 | 39,705
Significant Unobservable Inputs (Level 3) | Contingent Consideration |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis |  |
Liabilities |  | 9,106
Significant Unobservable Inputs (Level 3) | Long Term Contingent Consideration |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis |  |
Liabilities | $ 7,227 | $ 30,599

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