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Fair Value Measurements - Additional Information (Detail) - USD ($) | 9 Months Ended |
--- | --- | ---
Sep. 30, 2019 | Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Liquid investments, original maturities | 90 days |
Perpetual growth rate for deferred consideration | 1.50% | 1.50%
Discount rate for deferred consideration | 10.00% |
Minimum [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Gold forward-looking price range | $ 1,467 | $ 1,294
Maximum [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Gold forward-looking price range | $ 2,277 | $ 2,621

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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
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