Income Taxes - Additional Information (Detail) (USD $)	12 Months Ended
	Jan. 31, 2012	Jan. 31, 2011	Jan. 31, 2010	Jan. 31, 2009
Income Taxes [Line Items]
Increase Decrease In Income taxes Payable Current	$ 31,300,000
Deferred Tax Assets, Tax Deferred Expense, Compensation and Benefits, Employee Benefits	150,100,000
Income (Loss) from Continuing Operations before Income Taxes, Foreign	383,700,000	321,100,000	253,900,000
Deferred Tax Liability Not Recognized, Cumulative Amount of Temporary Difference	1,290,100,000
Deferred Tax Liability Not Recognized, Amount of Unrecognized Deferred Tax Liability	390,900,000
Net deferred tax assets	165,900,000	147,500,000
Foreign Income Tax Expense (Benefit), Continuing Operations	10,400,000	0	0
Income Tax Holiday, Income Tax Benefits Per Share	$ 0.046
Current Foreign Tax Expense (Benefit)	55,900,000	48,400,000	34,100,000
Valuation Allowance, Amount		4,900,000	20,200,000
Income Tax Reconciliation, Closure of Income Tax Audits and Changes in Uncertain Tax Positions		2,800,000	2,500,000
Gross unrecognized tax benefits	201,100,000	188,400,000	178,200,000	169,400,000
Amount of gross unrecognized tax benefits that would impact the effective tax rate, if recognized	187,800,000
Unrecognized Tax Benefits, Interest on Income Taxes Accrued	2,400,000	1,900,000	2,200,000
Deferred Federal Income Tax Expense (Benefit)	(34,500,000)	(8,200,000)	(33,000,000)
Valuation Allowance of Deferred Tax Assets California
Income Taxes [Line Items]
Valuation Allowance, Deferred Tax Asset, Change in Amount	(4,600,000)	(3,900,000)	(14,300,000)
Domestic Country
Income Taxes [Line Items]
Operating Loss Carryforwards	34,200,000
State and Local Jurisdiction
Income Taxes [Line Items]
Operating Loss Carryforwards	306,900,000
Research
Income Taxes [Line Items]
Tax Credit Carryforward, Amount	77,800,000
Change in Tax Status
Income Taxes [Line Items]
Current Foreign Tax Expense (Benefit)	4,000,000
California State Research
Income Taxes [Line Items]
Tax Credit Carryforward, Amount	34,300,000
Canadian
Income Taxes [Line Items]
Tax Credit Carryforward, Amount	50,100,000
Foreign Country
Income Taxes [Line Items]
Tax Credit Carryforward, Amount	$ 60,000,000
Minimum
Income Taxes [Line Items]
Operating Loss Carryforwards, Expiration Dates	2013
Minimum | Federal Research
Income Taxes [Line Items]
Tax Credit Carryforward, Expiration Dates	2013
Minimum | Canadian
Income Taxes [Line Items]
Tax Credit Carryforward, Expiration Dates	2023
Minimum | Foreign Country
Income Taxes [Line Items]
Tax Credit Carryforward, Expiration Dates	2020
Maximum
Income Taxes [Line Items]
Operating Loss Carryforwards, Expiration Dates	2032
Maximum | Federal Research
Income Taxes [Line Items]
Tax Credit Carryforward, Expiration Dates	2032
Maximum | Canadian
Income Taxes [Line Items]
Tax Credit Carryforward, Expiration Dates	2032
Maximum | Foreign Country
Income Taxes [Line Items]
Tax Credit Carryforward, Expiration Dates	2022