Financial Instruments Available for Sale Securities (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended	6 Months Ended
	Jul. 31, 2011	Jul. 31, 2012	Jan. 31, 2012
Financial Instruments [Abstract]
Proceeds from Sale and Maturity of Marketable Securities	$ 282.3	$ 389.4
Notional Amount of Foreign Currency Cash Flow Hedge Derivatives		382.9	419.6
Accumulated Other Comprehensive Income (Loss), Cumulative Changes in Net Gain (Loss) from Cash Flow Hedges, Effect Net of Tax		12.7	9.2
Notional Amount of Foreign Currency Derivative Instruments Not Designated as Hedging Instruments		22.1	75.1
Other than Temporary Impairment Losses, Investments		10.0
Gain (Loss) on Investments		$ 5.0