Summary of Significant Accounting Policies - Additional Information (Detail) (USD $)	9 Months Ended		12 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Jun. 30, 2013
Significant Accounting Policies [Line Items]
Other comprehensive income			$ (68,170,000)	$ (13,699,000)	$ (73,849,000)
Other comprehensive income, foreign currency translation adjustments			(64,641,000)	(11,910,000)	(69,832,000)
Money market fund			33,200,000	29,200,000
Term deposits, maximum maturity period (in months)			3 months
Term deposits			340,300,000	266,100,000
Term deposits, noncurrent			160,000	10,000
Depreciation and amortization expense			14,500,000	14,400,000	16,900,000
Favorable adjustment upon review of uncertain tax liabilities	240,000		1,090,000	240,000	3,500,000
Inflation growth rate			4.00%
Additional deferred tax assets and credit to tax expense						550,000
Reversal based on valuation allowance			430,000		600,000
Increase from update to apportionment methodology			1,590,000		1,300,000
Effective tax rate reconciliation resulting from certain adjustments			23.50%	22.80%	23.00%
Decrease in basic and diluted due to revisions in payment of tax			$ 0.04
Impact on earnings per share				$ 0	$ 0.10
Reversal of tax reserve due to reversal of previous position		2,600,000	0	240,000
Unrecognized Tax Benefits, Decreases Resulting From Reversal Of Valuation Allowance		600,000
Unrecognized Tax Benefits, Decreases Resulting From Reconciliation Of Tax Returns To Book Provision					1,200,000
Foreign exchange gain (loss)			9,000,000	1,300,000	8,700,000
Unutilized earned leave expense			5,100,000	4,900,000	5,600,000
Accrual for unutilized earned leave			19,100,000	17,900,000
Bank of America
Significant Accounting Policies [Line Items]
Term deposits			3,260,000
Punjab National Bank and Bank of India
Significant Accounting Policies [Line Items]
Term deposits			29,800,000
Bank Of India
Significant Accounting Policies [Line Items]
Term deposits			18,000,000	18,000,000
Minimum
Significant Accounting Policies [Line Items]
Rate of Inflation, maximum			4.00%
Maximum
Significant Accounting Policies [Line Items]
Rate of Inflation, maximum			11.00%
Prior Years
Significant Accounting Policies [Line Items]
Increase from update to apportionment methodology			600,000		800,000
Foreign Exchange Forward
Significant Accounting Policies [Line Items]
Foreign exchange forward contracts, notional amount			341,000,000	255,000,000	185,000,000
Foreign exchange forward contracts, minimum maturity date, months					1 month
Foreign exchange forward contracts, maximum maturity date					9 months
Derivative contracts expired			341,000,000	315,000,000	165,000,000
Loss on expiration of contracts			18,050,000	4,370,000	8,950,000
Foreign exchange forward contracts outstanding			0	0
Foreign exchange forward contracts, amount outstanding					60,000,000
Fair value of foreign exchange forward contracts					2,600,000
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			7 months	4 months
Foreign Exchange Forward | Client Contracts
Significant Accounting Policies [Line Items]
Loss on expiration of contracts			11,260,000	2,810,000	4,890,000
Foreign Exchange Forward | Intercompany Contracts
Significant Accounting Policies [Line Items]
Loss on expiration of contracts			$ 6,790,000	$ 1,560,000	$ 4,080,000