Summary of Significant Accounting Policies - Additional Information (Detail) (USD $)	3 Months Ended			9 Months Ended	12 Months Ended
	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Sep. 30, 2011	Dec. 31, 2012 M	Dec. 31, 2011	Dec. 31, 2010
Significant Accounting Policies [Line Items]
Other comprehensive income					$ 13,700,000	$ 73,800,000	$ 15,500,000
Other comprehensive income, foreign currency translation adjustments					11,900,000	69,800,000	13,900,000
Investments original maturity to be cash equivalents (in months)					3
Money market fund					29,200,000	17,600,000
Term deposits, maximum maturity period (in months)					3
Money market fund					266,100,000	190,800,000
Term deposits, noncurrent					10,000	100,000
Depreciation and amortization expense					14,400,000	16,900,000	14,400,000
Favorable adjustment upon review of uncertain tax liabiliti		900,000	3,200,000		240,000	3,500,000	1,280,000
Reversal of tax reserve due to reversal of previous position	300,000	0	300,000	2,600,000	240,000	3,460,000
Reversal of tax reserve due to reversal of a valuation allowance	600,000			600,000
Reversal from reconciliation of tax returns to book provision	1,200,000					1,200,000	500,000
Reversal based on valuation allowance						600,000
Increase from update to apportionment methodology						1,300,000
Impact on earnings per share						$ 0.10	$ 0.05
Deferred tax asset, change in amount							200,000
Foreign exchange gain (loss)					1,300,000	8,700,000	(2,000,000)
Unutilized earned leave expense					4,900,000	5,600,000	4,000,000
Accrual for unutilized earned leave					17,900,000	15,400,000
Bank Of India
Significant Accounting Policies [Line Items]
Money market fund					18,000,000
Bank Of India, Punjab National Bank, And ICICI
Significant Accounting Policies [Line Items]
Money market fund						43,700,000
Minimum
Significant Accounting Policies [Line Items]
Foreign currency rate translation							44.50
Maximum
Significant Accounting Policies [Line Items]
Foreign currency rate translation							46.20
Prior Years
Significant Accounting Policies [Line Items]
Increase from update to apportionment methodology						800,000
Carry Back Of Losses
Significant Accounting Policies [Line Items]
Deferred tax asset, change in amount							200,000
Foreign Exchange Forward
Significant Accounting Policies [Line Items]
Foreign exchange forward contracts, notional amount					255,000,000	185,000,000	165,000,000
Foreign exchange forward contracts, minimum maturity date, months						1 month	1 month
Foreign exchange forward contracts, maximum maturity date						9 months	4 months
Derivative contracts expired					315,000,000	165,000,000	125,000,000
Loss on expiration of contracts					4,370,000	8,950,000
Foreign exchange forward contracts, amount outstanding						60,000,000	40,000,000
Fair value of foreign exchange forward contracts						2,600,000
Gain on expiration of contracts							4,200,000
Foreign Exchange Forward | Minimum
Significant Accounting Policies [Line Items]
Foreign exchange forward contracts, minimum maturity date, months					1 month
Foreign Exchange Forward | Maximum
Significant Accounting Policies [Line Items]
Foreign exchange forward contracts, maximum maturity date					4 months
Foreign Exchange Forward | Client Contracts
Significant Accounting Policies [Line Items]
Loss on expiration of contracts					2,810,000	4,890,000
Gain on expiration of contracts							2,500,000
Foreign Exchange Forward | Intercompany Contracts
Significant Accounting Policies [Line Items]
Loss on expiration of contracts					1,560,000	4,080,000
Gain on expiration of contracts							1,700,000
Foreign Exchange Option
Significant Accounting Policies [Line Items]
Foreign exchange forward contracts, notional amount							$ 5,000,000
Foreign currency rate translation							44.51