Effects of Derivative Instruments on Condensed Consolidated Statements of Operations (Detail) (Foreign exchange contracts, USD $) In Millions	3 Months Ended
	Apr. 30, 2011	Apr. 30, 2010
Fair Value Hedging
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain (Loss) Recognized in Accumulated OCI on Derivatives (Effective Portion)	$ (9.6)	$ 10.9
Amount and Location of Gain (Loss) Reclassified from Accumulated OCI into Income (Effective Portion)	(1.9)	3.9
Fair Value Hedging | Net revenue
Derivative Instruments, Gain (Loss) [Line Items]
Amount and Location of Gain (Loss) Reclassified from Accumulated OCI into Income (Effective Portion)	(3.8)	3.4
Fair Value Hedging | Operating expenses
Derivative Instruments, Gain (Loss) [Line Items]
Amount and Location of Gain (Loss) Reclassified from Accumulated OCI into Income (Effective Portion)	1.9	0.5
Fair Value Hedging | Interest and other income, net
Derivative Instruments, Gain (Loss) [Line Items]
Amount and Location of Gain (Loss) Recognized in Income on Derivatives (Ineffective Portion and Amount Excluded from Effectiveness Testing)	(0.3)	(0.1)
Derivatives Not Designated as Hedging Instruments | Interest and other income, net
Derivative Instruments, Gain (Loss) [Line Items]
Amount and Location of Gain (Loss) Recognized in Income on Derivative	$ (1.7)	$ 1.7