Derivative Financial Instruments - Schedule of aggregate notional principal amounts of outstanding derivative financial instruments with related balance sheet exposure (Detail) - USD ($)	Sep. 30, 2021	Dec. 31, 2020
Derivative [Line Items]
Derivative financial instrument, balance sheet exposure asset (liability)	$ 103,000	$ (13,272,000)
United States Dollars (sell) Indian Rupees (buy)
Derivative [Line Items]
Derivative instrument notional principal amount	1,022,500,000	1,150,000,000
Derivative financial instrument, balance sheet exposure asset (liability)	13,564,000	15,207,000
United States Dollars (sell) Mexican Peso (buy)
Derivative [Line Items]
Derivative instrument notional principal amount	13,000,000	17,500,000
Derivative financial instrument, balance sheet exposure asset (liability)	(130,000)	716,000
United States Dollars (sell) Philippines Peso (buy)
Derivative [Line Items]
Derivative instrument notional principal amount	96,750,000	67,200,000
Derivative financial instrument, balance sheet exposure asset (liability)	(3,078,000)	1,332,000
Euro (sell) United States Dollars (buy)
Derivative [Line Items]
Derivative instrument notional principal amount	73,954,000	96,651,000
Derivative financial instrument, balance sheet exposure asset (liability)	963,000	(5,659,000)
Singapore Dollars (buy) United States Dollars (sell)
Derivative [Line Items]
Derivative instrument notional principal amount	10,153,000	10,153,000
Derivative financial instrument, balance sheet exposure asset (liability)	(237,000)	66,000
Euro (sell) Romanian Leu (buy)
Derivative [Line Items]
Derivative instrument notional principal amount	27,833,000	29,489,000
Derivative financial instrument, balance sheet exposure asset (liability)	(104,000)	(22,000)
Japanese Yen (sell) Chinese Renminbi (buy)
Derivative [Line Items]
Derivative instrument notional principal amount	4,431,000	19,230,000
Derivative financial instrument, balance sheet exposure asset (liability)	603,000	473,000
United States Dollars (sell) Hungarian Font (buy)
Derivative [Line Items]
Derivative instrument notional principal amount	21,900,000	30,000,000
Derivative financial instrument, balance sheet exposure asset (liability)	(722,000)	904,000
Hungarian Font (Sell) Euro (buy)
Derivative [Line Items]
Derivative instrument notional principal amount	9,857,000	10,444,000
Derivative financial instrument, balance sheet exposure asset (liability)	(93,000)	61,000
Australian Dollars (sell) Indian Rupees (buy)
Derivative [Line Items]
Derivative instrument notional principal amount	80,685,000	140,525,000
Derivative financial instrument, balance sheet exposure asset (liability)	546,000	(7,670,000)
Pound Sterling (sell) United States Dollar (buy)
Derivative [Line Items]
Derivative instrument notional principal amount	24,955,000	0
Derivative financial instrument, balance sheet exposure asset (liability)	766,000	0
Interest rate swaps (floating to fixed)
Derivative [Line Items]
Derivative instrument notional principal amount	467,107,000	488,022,000
Derivative financial instrument, balance sheet exposure asset (liability)	$ (11,975,000)	$ (18,680,000)

Fair value of credit risk derivative asset after deduction of credit risk derivative liability.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4K
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=121590274&loc=SL5708775-113959

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Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1B
-URI http://asc.fasb.org/extlink&oid=121590274&loc=SL5580258-113959

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1A
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=121590274&loc=SL5579245-113959

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