Derivative Financial Instruments (Details Textual) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jul. 31, 2012 USD ($)	Jul. 31, 2011 USD ($) oz	Jul. 31, 2012 USD ($)	Jul. 31, 2011 USD ($) oz	Jul. 31, 2012 CHF
Derivative Financial Instruments (Textual) [Abstract]
Net forward contracts hedging portfolio					38.0
Commodity futures contracts hedging portfolio		4,400		4,400
Derivative financial instruments net losses	1.0	0.8
Tax portion of derivative financial instruments net losses	1.0	1.0
Length of time of the company hedges	24 months
Net gains on derivative financial instruments	0	0.3	0	0.6
Tax portion of derivative financial instruments	0	0.1
Charge related to its assessment derivative hedge portfolio