Summary of Significant Accounting Policies- Additional Information (Detail) $ / shares in Units, $ in Thousands	1 Months Ended	3 Months Ended	12 Months Ended
	Sep. 30, 2012 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($) Derivative	Dec. 31, 2013 USD ($) Derivative $ / shares	Jun. 30, 2013 USD ($)
Significant Accounting Policies [Line Items]
Other comprehensive income			$ (49,365)	$ (31,941)	$ (68,170)
Other comprehensive income, foreign currency translation adjustments			45,400	32,400	64,700
Out-of-period adjustment relating to the past period adjustments			3,000
Money market fund		$ 500,500	500,500	197,700
Fixed Maturity Plans (FMPs) of mutual funds, at cost		0	0	15,886
Term deposits		413,600	413,600	466,600
Non current term deposits with banks		77	77	105
Depreciation and amortization expense			15,600	16,100	14,500
Favorable adjustment upon review of uncertain tax liabilities	$ 240			1,200	$ 1,090
Additional tax charge on account of tax dispute				860
Tax charges related to deferred tax assets on long-term gain on investment				1,630
Valuation allowances		5,454	5,454	2,616
Inflation growth rate					4.00%
Additional deferred tax assets and credit to tax expense						$ 550
Reversal based on valuation allowance					$ 430
Increase from update to apportionment methodology					$ 1,590
Decrease in basic and diluted due to revisions in payment of tax | $ / shares					$ 0.04
Foreign exchange gain (loss)			18,100	10,700	$ 9,000
Out-of-period adjustment				3,000
Unutilized earned leave expense			5,300	5,400	5,100
Accrual for unutilized earned leave		22,400	22,400	21,500
Foreign Currency Translation Adjustments
Significant Accounting Policies [Line Items]
Other comprehensive income			(45,736)	(31,994)	(71,437)
Out-of-period adjustment				3,000
Prior Years
Significant Accounting Policies [Line Items]
Increase from update to apportionment methodology					$ 600
Minimum Alternate Tax (MAT)
Significant Accounting Policies [Line Items]
Valuation allowances			840
Valuation allowances		840	840	880
India Tax Authority
Significant Accounting Policies [Line Items]
Favorable adjustment upon review of uncertain tax liabilities			1,100
Local Jurisdiction
Significant Accounting Policies [Line Items]
Favorable adjustment upon review of uncertain tax liabilities		1,200	1,200
Minimum
Significant Accounting Policies [Line Items]
Rate of Inflation					4.00%
Maximum
Significant Accounting Policies [Line Items]
Rate of Inflation					11.00%
Foreign Exchange Forward
Significant Accounting Policies [Line Items]
Foreign exchange forward contracts, notional amount				160,000	$ 341,000
Derivative contracts expired				160,000	$ 341,000
Gain on expiration of contracts				$ 4,560
Foreign exchange forward contracts outstanding | Derivative				0	0
Loss on expiration of contracts					$ 18,050
Foreign Exchange Forward | Client Contracts
Significant Accounting Policies [Line Items]
Loss on expiration of contracts					11,260
Foreign Exchange Forward | Intercompany Contracts
Significant Accounting Policies [Line Items]
Loss on expiration of contracts					$ 6,790
Foreign Exchange Forward | Minimum
Significant Accounting Policies [Line Items]
Foreign exchange forward contracts, minimum maturity date, months				1 month	1 month
Foreign Exchange Forward | Maximum
Significant Accounting Policies [Line Items]
Foreign exchange forward contracts, maximum maturity date				6 months	7 months
Restricted Deposits
Significant Accounting Policies [Line Items]
Term deposits		$ 600	$ 600	$ 530