Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands		3 Months Ended
		Apr. 30, 2016	Apr. 30, 2015
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance		$ 68,505	$ 98,854
Other comprehensive income / (loss) before reclassifications		17,792	(3,804)
Amounts reclassified from accumulated other comprehensive (loss) / income	[1]	(126)	171
Net current-period other comprehensive income / (loss)		17,666	(3,633)
Ending Balance		86,171	95,221
Currency Translation Adjustments
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance		68,265	98,642
Other comprehensive income / (loss) before reclassifications		17,892	(3,135)
Net current-period other comprehensive income / (loss)		17,892	(3,135)
Ending Balance		86,157	95,507
Available-for-sale securities
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance		189	211
Other comprehensive income / (loss) before reclassifications		6	10
Net current-period other comprehensive income / (loss)		6	10
Ending Balance		195	221
Net Unrealized Income (Loss) On Hedging Contracts
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance		51	1
Other comprehensive income / (loss) before reclassifications		(106)	(679)
Amounts reclassified from accumulated other comprehensive (loss) / income	[1]	(126)	171
Net current-period other comprehensive income / (loss)		(232)	(508)
Ending Balance		$ (181)	$ (507)

[1] Amounts reclassified to earnings in the Consolidated Statements of Operations.