Income Taxes - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	0 Months Ended	3 Months Ended					9 Months Ended		12 Months Ended													12 Months Ended		0 Months Ended	3 Months Ended			12 Months Ended
	Jul. 13, 2011	Dec. 31, 2013	Sep. 30, 2013	Mar. 31, 2013	Sep. 30, 2012	Sep. 30, 2010	Sep. 30, 2012	Sep. 30, 2011	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2005	Dec. 31, 2004	Dec. 31, 2003	Dec. 31, 2002	Dec. 31, 2013 Minimum Alternate Tax (MAT)	Dec. 31, 2009 Software Development Entity	Apr. 30, 2008 Tax Exemption Period Entity	Mar. 31, 2013 Mumbai Tax Exemption Period Entity	Mar. 31, 2012 Mumbai Completion of Tax Holiday Period Entity	Dec. 31, 2013 Prior Years	Dec. 31, 2011 Prior Years	Apr. 30, 2008 Three Units in Mumbai First Five Years	Mar. 31, 2013 Three Units in Mumbai First Five Years	Mar. 31, 2013 Unit in Chennai First Five Years	Dec. 31, 2013 Other Disputes	Dec. 31, 2013 Certain Units In Sez First Five Years	Dec. 31, 2013 Certain Units In Sez Additional Two Years	Dec. 31, 2013 Certain Units In Sez Additional Three Years	Dec. 31, 2013 New Units In Sez First Five Years	Dec. 31, 2013 New Units In Sez Next Five Years	Dec. 31, 2013 New Units In Sez Another Five Years
Income Taxes [Line Items]
Corporate income taxes, exemption percentage																								100.00%	50.00%	100.00%		100.00%	50.00%	50.00%	100.00%	50.00%	50.00%
Number of units																		1	4	6	1
Exemption from corporate income taxes									10 years
Corporate income taxes, years									15 years
Benefit of tax Holiday under Indian Income Tax									$ 32.2	$ 24.6	$ 19.1
Accrued taxes, likely amount		212.1							212.1
Statutory rate									35.00%	35.00%	35.00%
Effective income tax rate									23.10%	22.70%	20.40%
Income taxes paid against liabilities for unrecognized tax benefits		26.37							26.37	20.58
Liabilities for unrecognized tax benefits		30.22							30.22	24.94	18.41
Expense recognized for accrued interest and penalties									0.17	1.46
Accrued interest and penalties related to unrecognized tax benefits		1.39							1.39	1.40
Unrecognized tax benefits, tax disputes									1.52
Unrecognized tax benefits, potential tax disputes									2.91
Favorable adjustment upon review of tax liabilities							0.24		1.09	0.24	3.50
Reversal based on valuation allowance									0.43		0.60
Increase from update to apportionment methodology									1.59		1.30											0.60	0.80
Effective tax rate reconciliation resulting from certain adjustments									23.50%	22.80%	23.00%
Reversal of tax reserve due to reversal of previous position								2.60	0	0.24
Unrecognized Tax Benefits, Decreases Resulting From Reversal Of Valuation Allowance								0.6
Unrecognized Tax Benefits, Decreases Resulting From Reconciliation Of Tax Returns To Book Provision											1.2
Unrecognized Indian income tax liabilities															4.64	4.64											1.54
Income tax liability recognized													0.73	0.73													0.79
Income tax adjustments provision reversal												0.33
Income tax audit, service tax objection amount		0.45			0.50	3.85
Service tax audit objection received	3.0
Closure of service tax audit objection amount		0.85							0.85
Service tax refund			0.13	0.15
Service tax return with show cause notice									1.97
Service tax penalty and interest demanded by tax department		3.80							3.80
Interest percentage on service tax penalty									18.00%
Local tax liability gross		4.5							4.5	4.3
Local tax liability net										2.7
Minimum alternate tax credit expiration period																	10 years
Minimum Alternate Tax Credit																	$ 20.46