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Financial Derivatives and Hedging Activities - Outstanding Derivatives Used to Hedge Foreign Exchange Risks (Detail) | Sep. 30, 2021 PHP (₱) | Sep. 30, 2021 EUR (€) | Sep. 30, 2021 USD ($) | Sep. 30, 2021 CAD ($) | Sep. 30, 2021 GBP (£) | Dec. 31, 2020 PHP (₱) | Dec. 31, 2020 EUR (€) | Dec. 31, 2020 USD ($) | Dec. 31, 2020 CAD ($) | Dec. 31, 2020 GBP (£)
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Cash Flow Hedges | Philippine Peso / Euro | Designated as Hedging | Sell Notional |  |  |  |  |  |  |  |  |  |
Derivative Instruments And Hedging Activities Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |
Derivative notional amount | ₱ | ₱ 13,514,000 |  |  |  |  | ₱ 18,522,000 |  |  |  |
Cash Flow Hedges | Euro / British Pound | Designated as Hedging | Sell Notional |  |  |  |  |  |  |  |  |  |
Derivative Instruments And Hedging Activities Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |
Derivative notional amount | € |  | € 19,318,000 |  |  |  |  | € 18,638,000 |  |  |
Cash Flow Hedges | U.S. Dollar / British Pound | Designated as Hedging | Sell Notional |  |  |  |  |  |  |  |  |  |
Derivative Instruments And Hedging Activities Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |
Derivative notional amount |  |  | $ 10,331,000 |  |  |  |  | $ 0 |  |
Cash Flow Hedges | U.S. Dollar / Euro | Designated as Hedging | Sell Notional |  |  |  |  |  |  |  |  |  |
Derivative Instruments And Hedging Activities Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |
Derivative notional amount |  |  | 1,022,000 |  |  |  |  | 1,041,000 |  |
Cash Flow Hedges | Canadian Dollar / U.S. Dollar | Designated as Hedging | Sell Notional |  |  |  |  |  |  |  |  |  |
Derivative Instruments And Hedging Activities Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |
Derivative notional amount |  |  |  | $ 0 |  |  |  |  | $ 70,000 |
Cash Flow Hedges | Euro / Philippine Peso | Designated as Hedging | Buy Notional |  |  |  |  |  |  |  |  |  |
Derivative Instruments And Hedging Activities Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |
Derivative notional amount | ₱ | 876,006,000 |  |  |  |  | 853,686,000 |  |  |  |
Cash Flow Hedges | British Pound / Philippine Peso | Designated as Hedging | Buy Notional |  |  |  |  |  |  |  |  |  |
Derivative Instruments And Hedging Activities Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |
Derivative notional amount | ₱ | ₱ 1,149,365,000 |  |  |  |  | ₱ 1,081,791,000 |  |  |  |
Cash Flow Hedges | Euro / U.S. Dollar | Designated as Hedging | Buy Notional |  |  |  |  |  |  |  |  |  |
Derivative Instruments And Hedging Activities Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |
Derivative notional amount |  |  | 93,797,000 |  |  |  |  | 69,324,000 |  |
Cash Flow Hedges | U.S. Dollar / Canadian Dollar | Designated as Hedging | Buy Notional |  |  |  |  |  |  |  |  |  |
Derivative Instruments And Hedging Activities Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |
Derivative notional amount |  |  |  | $ 33,345,000 |  |  |  |  | $ 34,847,000 |
Cash Flow Hedges | British Pound / U.S. Dollar | Designated as Hedging | Buy Notional |  |  |  |  |  |  |  |  |  |
Derivative Instruments And Hedging Activities Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |
Derivative notional amount |  |  | 851,000 |  |  |  |  | 0 |  |
Foreign Currency Hedges | Euro / British Pound | Not Designated as Hedging | Sell Notional |  |  |  |  |  |  |  |  |  |
Derivative Instruments And Hedging Activities Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |
Derivative notional amount | € |  | 0 |  |  |  |  | 600,000 |  |  |
Foreign Currency Hedges | U.S. Dollar / British Pound | Not Designated as Hedging | Sell Notional |  |  |  |  |  |  |  |  |  |
Derivative Instruments And Hedging Activities Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |
Derivative notional amount |  |  | 22,050,000 |  |  |  |  | 25,250,000 |  |
Foreign Currency Hedges | Euro / U.S. Dollar | Not Designated as Hedging | Buy Notional |  |  |  |  |  |  |  |  |  |
Derivative Instruments And Hedging Activities Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |
Derivative notional amount |  |  | 17,200,000 |  |  |  |  | 7,500,000 |  |
Foreign Currency Hedges | British Pound / Euro | Not Designated as Hedging | Sell Notional |  |  |  |  |  |  |  |  |  |
Derivative Instruments And Hedging Activities Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |
Derivative notional amount | £ |  |  |  |  | £ 2,400,000 |  |  |  |  | £ 1,900,000
Foreign Currency Hedges | British Pound / Euro | Not Designated as Hedging | Buy Notional |  |  |  |  |  |  |  |  |  |
Derivative Instruments And Hedging Activities Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |
Derivative notional amount | € |  | 1,200,000 |  |  |  |  | 0 |  |  |
Foreign Currency Hedges | U.S. Dollar / Swiss Franc | Not Designated as Hedging | Sell Notional |  |  |  |  |  |  |  |  |  |
Derivative Instruments And Hedging Activities Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |
Derivative notional amount |  |  | $ 1,300,000 |  |  |  |  | $ 0 |  |
Foreign Currency Hedges | British Pound / Swiss Franc | Not Designated as Hedging | Sell Notional |  |  |  |  |  |  |  |  |  |
Derivative Instruments And Hedging Activities Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |
Derivative notional amount | £ |  |  |  |  | £ 750,000 |  |  |  |  | £ 0
Foreign Currency Hedges | Euro / Swiss Franc | Not Designated as Hedging | Sell Notional |  |  |  |  |  |  |  |  |  |
Derivative Instruments And Hedging Activities Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |
Derivative notional amount | € |  | € 1,400,000 |  |  |  |  | € 0 |  |  |

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