Pre-tax Effect of Derivative Instruments in Cash Flow Hedging Relationships on Income and Other Comprehensive Income (OCI) (Detail) (Cash Flow Hedging, USD $) In Thousands, unless otherwise specified	9 Months Ended
	Oct. 31, 2011	Oct. 31, 2010
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in OCI on Derivatives (Effective Portion)	$ 147	$ (3,117)
Gain (Loss) Reclassified from Accumulated OCI into Income (Effective Portion)	215	(4,736)
Gain (Loss) Recognized in Income on Derivatives (Ineffective Portion and Amount Excluded from Effectiveness Testing)	65	46
Cash flow forwards
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in OCI on Derivatives (Effective Portion)	147	(3,117)
Cash flow forwards | Revenues
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Reclassified from Accumulated OCI into Income (Effective Portion)	(859)	(657)
Cash flow forwards | Operating Expenses
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Reclassified from Accumulated OCI into Income (Effective Portion)	1,074	(4,079)
Cash flow forwards | Other income (expense)
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in Income on Derivatives (Ineffective Portion and Amount Excluded from Effectiveness Testing)	$ 65	$ 46