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Financial Derivatives and Hedging Activities - Outstanding Derivatives Used to Hedge Foreign Exchange Risks (Detail) | Mar. 31, 2019 USD ($) | Mar. 31, 2019 EUR (€) | Mar. 31, 2019 PHP (₱) | Mar. 31, 2019 CAD ($) | Mar. 31, 2019 GBP (£) | Dec. 31, 2018 USD ($) | Dec. 31, 2018 EUR (€) | Dec. 31, 2018 PHP (₱) | Dec. 31, 2018 CAD ($) | Dec. 31, 2018 GBP (£)
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Cash Flow Hedges [Member] | Philippine Peso / British Pound [Member] | Designated as Hedging [Member] | Sell Notional [Member] |  |  |  |  |  |  |  |  |  |
Derivative Instruments And Hedging Activities Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |
Derivative notional amount | ₱ |  |  |  |  |  |  |  | ₱ 13,140,000 |  |
Cash Flow Hedges [Member] | Euro / British Pound [Member] | Designated as Hedging [Member] | Sell Notional [Member] |  |  |  |  |  |  |  |  |  |
Derivative Instruments And Hedging Activities Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |
Derivative notional amount | € |  | € 15,103,000 |  |  |  |  | € 15,250,000 |  |  |
Cash Flow Hedges [Member] | Philippine Peso Euro [Member] | Designated as Hedging [Member] | Sell Notional [Member] |  |  |  |  |  |  |  |  |  |
Derivative Instruments And Hedging Activities Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |
Derivative notional amount | ₱ |  |  | ₱ 14,625,000 |  |  |  |  | 16,446,000 |  |
Cash Flow Hedges [Member] | Euro / Philippine Peso [Member] | Designated as Hedging [Member] | Buy Notional [Member] |  |  |  |  |  |  |  |  |  |
Derivative Instruments And Hedging Activities Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |
Derivative notional amount | ₱ |  |  | 1,037,683,000 |  |  |  |  | 1,069,006,000 |  |
Cash Flow Hedges [Member] | British Pound / Philippine Peso [Member] | Designated as Hedging [Member] | Buy Notional [Member] |  |  |  |  |  |  |  |  |  |
Derivative Instruments And Hedging Activities Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |
Derivative notional amount | ₱ |  |  | ₱ 964,867,000 |  |  |  |  | ₱ 980,137,000 |  |
Cash Flow Hedges [Member] | Euro / U.S. Dollar [Member] | Designated as Hedging [Member] | Buy Notional [Member] |  |  |  |  |  |  |  |  |  |
Derivative Instruments And Hedging Activities Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |
Derivative notional amount | $ | $ 94,646,000 |  |  |  |  | $ 76,417,000 |  |  |  |
Cash Flow Hedges [Member] | U.S. Dollar / Canadian Dollar [Member] | Designated as Hedging [Member] | Buy Notional [Member] |  |  |  |  |  |  |  |  |  |
Derivative Instruments And Hedging Activities Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |
Derivative notional amount | $ |  |  |  | $ 34,304,000 |  |  |  |  | $ 35,154,000 |
Cash Flow Hedges [Member] | U.S Dollar / Euro [Member] | Designated as Hedging [Member] | Sell Notional [Member] |  |  |  |  |  |  |  |  |  |
Derivative Instruments And Hedging Activities Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |
Derivative notional amount | € |  | 1,328,000 |  |  |  |  | 88,000 |  |  |
Cash Flow Hedges [Member] | British Pound / Euro [Member] | Designated as Hedging [Member] | Buy Notional [Member] |  |  |  |  |  |  |  |  |  |
Derivative Instruments And Hedging Activities Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |
Derivative notional amount | € |  |  |  |  |  |  | 216,000 |  |  |
Foreign Currency Hedges [Member] | Euro / U.S. Dollar [Member] | Not Designated as Hedging [Member] | Buy Notional [Member] |  |  |  |  |  |  |  |  |  |
Derivative Instruments And Hedging Activities Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |
Derivative notional amount | $ | 15,000,000 |  |  |  |  | 11,000,000 |  |  |  |
Foreign Currency Hedges [Member] | British Pound / Euro [Member] | Not Designated as Hedging [Member] | Sell Notional [Member] |  |  |  |  |  |  |  |  |  |
Derivative Instruments And Hedging Activities Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |
Derivative notional amount | £ |  |  |  |  | £ 3,000,000 |  |  |  |  | £ 2,000,000
Foreign Currency Hedges [Member] | British Pound / Euro [Member] | Not Designated as Hedging [Member] | Buy Notional [Member] |  |  |  |  |  |  |  |  |  |
Derivative Instruments And Hedging Activities Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |
Derivative notional amount | € |  | € 4,000,000 |  |  |  |  | € 8,000,000 |  |  |
Foreign Currency Hedges [Member] | U.S. Dollar / British Pound [Member] | Not Designated as Hedging [Member] | Sell Notional [Member] |  |  |  |  |  |  |  |  |  |
Derivative Instruments And Hedging Activities Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |
Derivative notional amount | $ | $ 18,000,000 |  |  |  |  | $ 25,500,000 |  |  |  |

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