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 (£)
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