Accumulated Other Comprehensive (Loss) / Income (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Apr. 30, 2013	Apr. 30, 2012
Components of accumulated other comprehensive (loss) / income
Begining Balance	$ 102,271	$ 97,922
Other comprehensive (loss) / income before reclassifications	(5,196)	3,523
Amounts reclassified from accumulated other comprehensive income
Net current-period other comprehensive (loss) / income	(5,196)	3,523
Ending Balance	97,075	101,445
Currency Translation Adjustments
Components of accumulated other comprehensive (loss) / income
Begining Balance	102,220	98,842
Other comprehensive (loss) / income before reclassifications	(5,197)	3,500
Amounts reclassified from accumulated other comprehensive income
Net current-period other comprehensive (loss) / income	(5,197)	3,500
Ending Balance	97,023	102,342
Net Unrealized Gains on Investments
Components of accumulated other comprehensive (loss) / income
Begining Balance	51	69
Other comprehensive (loss) / income before reclassifications	1	23
Amounts reclassified from accumulated other comprehensive income
Net current-period other comprehensive (loss) / income	1	23
Ending Balance	52	92
Net Unrealized (Loss) On Hedging Contracts
Components of accumulated other comprehensive (loss) / income
Begining Balance		(989)
Other comprehensive (loss) / income before reclassifications
Amounts reclassified from accumulated other comprehensive income
Net current-period other comprehensive (loss) / income
Ending Balance		$ (989)