Derivative Financial Instruments (Narrative) (Details)			3 Months Ended
	Apr. 30, 2015 USD ($)	Jan. 31, 2015 USD ($)	Apr. 30, 2015 Net Investment Hedging [Member] United Kingdom [Member] GBP (£)	Apr. 30, 2015 Net Investment Hedging [Member] JAPAN JPY (¥)	Apr. 30, 2015 Designated as Hedging Instrument [Member] Net Investment Hedging [Member] United Kingdom [Member] GBP (£)	Apr. 30, 2015 Designated as Hedging Instrument [Member] Net Investment Hedging [Member] JAPAN JPY (¥)
Derivative [Line Items]
Derivative, Collateral, Obligation to Return Cash	$ 324,000,000	$ 323,000,000
Threshold of derivative liability position requiring cash collateral	150,000,000
Debt designated as Japanese net investment hedge			£ 2,500,000,000	¥ 100,000,000,000	£ 2,500,000,000	¥ 100,000,000,000