Financial Instruments Available for Sale Securities (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Apr. 30, 2013	Apr. 30, 2012	Jan. 31, 2013
Financial Instruments [Abstract]
Proceeds from Sale and Maturity of Marketable Securities	$ 197.0	$ 177.3
Notional Amount of Foreign Currency Cash Flow Hedge Derivatives	354.6		359.8
Accumulated Other Comprehensive Income (Loss), Cumulative Changes in Net Gain (Loss) from Cash Flow Hedges, Effect Net of Tax	12.7		2.8
Notional Amount of Foreign Currency Derivative Instruments Not Designated as Hedging Instruments	44.4		78.4
Other than Temporary Impairment Losses, Investments	0
Gain (Loss) on Investments	$ (0.2)	$ 0