Derivative Financial Instruments (Narrative) (Details)			9 Months Ended
	Oct. 31, 2014 USD ($)	Jan. 31, 2014 USD ($)	Oct. 31, 2014 Cash Flow Hedging [Member] USD ($)	Oct. 31, 2014 Net Investment Hedging [Member] United Kingdom [Member] GBP (£)	Jan. 31, 2014 Net Investment Hedging [Member] United Kingdom [Member] GBP (£)	Oct. 31, 2014 Net Investment Hedging [Member] JAPAN JPY (¥)	Jan. 31, 2014 Net Investment Hedging [Member] JAPAN JPY (¥)
Derivative [Line Items]
Derivative Liability, Collateral, Right to Reclaim Cash, Offset	$ 337,000,000	$ 641,000,000
Threshold of derivative liability position requiring cash collateral	150,000,000
Debt designated as United Kingdom net investment hedge				2,500,000,000	2,500,000,000
Debt designated as Japanese net investment hedge						100,000,000,000	200,000,000,000
Derivative, Cash Received on Hedge			$ 22,000,000