Financial Instruments Effects of Derivative Instruments on Condensed Consolidated Statements of Operations (Details) (USD $)	3 Months Ended		6 Months Ended
	Jul. 31, 2012	Jul. 31, 2011	Jul. 31, 2012	Jul. 31, 2011
Derivative Instruments, Gain (Loss) [Line Items]
Net Income (Loss) Attributable to Parent	$ 64,600,000	$ 71,200,000	$ 143,500,000	$ 140,500,000
Designated as Hedging Instrument [Member] | Foreign Exchange Contract [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain (loss) recognized in accumulated other comprehensive income on derivatives (effective portion)	10,600,000	7,000,000	12,100,000	(2,600,000)
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	3,700,000	(1,300,000)	8,500,000	(3,200,000)
Sales [Member] | Designated as Hedging Instrument [Member] | Foreign Exchange Contract [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	6,100,000	(3,800,000)	12,400,000	(7,600,000)
Operating Expense [Member] | Designated as Hedging Instrument [Member] | Foreign Exchange Contract [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	(2,400,000)	2,500,000	(3,900,000)	4,400,000
Interest and other income (expense), net [member] | Designated as Hedging Instrument [Member] | Foreign Exchange Contract [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Interest and other income (expense), net	0	300,000	100,000	0
Interest and other income (expense), net [member] | Not Designated as Hedging Instrument [Member] | Foreign Exchange Contract [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Interest and other income, net	$ 0	$ 3,700,000	$ 1,000,000	$ 2,000,000