Derivative Instruments and Foreign Currency Exposure (Details ) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jul. 31, 2012	Jul. 31, 2011	Jul. 31, 2012	Apr. 30, 2012	Jul. 31, 2011	Apr. 30, 2011	Jan. 31, 2012
Derivatives not designated as hedging instruments, Foreign Exchange Forward Contracts
Notional Value in USD	$ 22,822	$ 3,635	$ 22,822	$ 25,326	$ 3,635	$ 6,506
Gain and loss reported in current operating income (expense)	2	14		(56)		(172)
Derivatives designated as hedging instruments, Asset Derivative from Foreign Currency Cash Flow Hedge
Notional Value in USD	8,719		8,719				6,904
Gain and loss reported in equity as other comprehensive income	(108)		(108)				123
Effect of Derivative on Income Statement from Foreign Currency Cash Flow Hedge
Gain reclassed from other comprehensive income into current earnings during three months ended April 30, 2012 reported in operating income			$ 10		$ 32