Financial Instruments Available for Sale Securities Gain/Loss Activity (Details) (USD $) In Millions, unless otherwise specified	6 Months Ended
Jul. 31, 2013	Jul. 31, 2012	Jan. 31, 2013
Financial Instruments [Abstract]
Proceeds from Sale and Maturity of Marketable Securities	$ 447.0	$ 389.4
Accumulated Other Comprehensive Income (Loss), Cumulative Changes in Net Gain (Loss) from Cash Flow Hedges, Effect Net of Tax	7.7		2.8
Other than Temporary Impairment Losses, Investments	0
Gain (Loss) on Investments	$ (0.2)	$ 5.0

Accumulated change, net of tax, in accumulated gains and losses from derivative instruments designated and qualifying as the effective portion of cash flow hedges. Includes an entity's share of an equity investee's Increase or Decrease in deferred hedging gains or losses.

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This item represents the net total realized and unrealized gain (loss) included in earnings for the period as a result of selling or holding marketable securities categorized as trading, available-for-sale, or held-to-maturity, including the unrealized holding gain (loss) of held-to-maturity securities transferred to the trading security category and the cumulative unrealized gain (loss) which was included in other comprehensive income (a separate component of shareholders' equity) for available-for-sale securities transferred to trading securities during the period. Additionally, this item would include any gains (losses) realized during the period from the sale of investments accounted for under the cost method of accounting and losses recognized for other than temporary impairments (OTTI) of the subject investments.

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