Financial Derivatives and Hedging Activities - Outstanding Derivatives Used to Hedge Foreign Exchange Risks (Detail)	Sep. 30, 2019 USD ($)	Sep. 30, 2019 EUR (€)	Sep. 30, 2019 PHP (₱)	Sep. 30, 2019 CAD ($)	Sep. 30, 2019 GBP (£)	Dec. 31, 2018 USD ($)	Dec. 31, 2018 EUR (€)	Dec. 31, 2018 PHP (₱)	Dec. 31, 2018 CAD ($)	Dec. 31, 2018 GBP (£)
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 | €		€ 17,428,000					€ 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 | ₱			₱ 6,784,000					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 | ₱			889,778,000					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 | ₱			₱ 1,083,507,000					₱ 980,137,000
Cash Flow Hedges [Member] | U.S. Dollar / Canadian Dollar [Member] | Designated as Hedging [Member] | Sell Notional [Member]
Derivative Instruments And Hedging Activities Disclosures [Line Items]
Derivative notional amount	$ 1,850,000
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				$ 34,934,000					$ 35,154,000
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	87,872,000					$ 76,417,000
Cash Flow Hedges [Member] | Canadian Dollar / U.S. Dollar [Member] | Designated as Hedging [Member] | Buy Notional [Member]
Derivative Instruments And Hedging Activities Disclosures [Line Items]
Derivative notional amount	1,850,000
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	6,859,000					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	12,000,000					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 | €		€ 9,000,000					€ 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	$ 26,000,000					$ 25,500,000