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Accounts Receivable, Net of Allowance for Credit Losses - Allowance for credit losses (Detail) - USD ($) $ in Thousands | 9 Months Ended | 12 Months Ended
--- | --- | ---
Sep. 30, 2021 | Dec. 31, 2020
Provisions For Doubtful Accounts [Line Items] |  |
Opening balance | $ 27,707 | $ 29,969
Additions due to acquisitions | 0 | 200
Additions charged/reversal released to cost and expense | 2,953 | 3,307
Deductions/effect of exchange rate fluctuations | (1,133) | (9,954)
Closing balance | $ 29,527 | 27,707
Cumulative Effect, Period of Adoption, Adjustment |  |
Provisions For Doubtful Accounts [Line Items] |  |
Opening balance |  | 4,185
Cumulative Effect, Period of Adoption, Adjusted Balance |  |
Provisions For Doubtful Accounts [Line Items] |  |
Opening balance |  | $ 34,154

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