Derivative Financial Instruments (Narrative) (Details)						9 Months Ended					9 Months Ended
	Oct. 31, 2012 USD ($)	Jan. 31, 2012 GBP (£)	Jan. 31, 2012 JPY (¥)	Oct. 31, 2012 Netting and Collateral [Member] USD ($)	Jan. 31, 2012 Netting and Collateral [Member] USD ($)	Oct. 31, 2012 Fair Value Hedging [Member]	Oct. 31, 2012 Net Investment Hedging [Member]	Oct. 31, 2012 Net Investment Hedging [Member] United Kingdom and Japan [Member]	Oct. 31, 2012 Net Investment Hedging [Member] United Kingdom [Member] GBP (£)	Oct. 31, 2012 Net Investment Hedging [Member] JAPAN JPY (¥)	Oct. 31, 2012 Cash Flow Hedging [Member] Interest Rate Swap [Member]	Oct. 31, 2012 Cash Flow Hedging [Member] Cross Currency Interest Rate Contract [Member]
Derivative [Line Items]
Derivative, Collateral, Obligation to Return Cash				$ 368,000,000	$ 387,000,000
Threshold of derivative liability position requiring cash collateral	150,000,000
Debt designated as United Kingdom net investment hedge		3,000,000,000							3,000,000,000
Debt designated as Japanese net investment hedge			¥ 275,000,000,000							¥ 275,000,000,000
Investment maturity date range start						Apr. 30, 2013	Oct. 30, 2023	Jan. 31, 2013			Aug. 30, 2013	Sep. 30, 2029
Investment maturity date range end						May 31, 2014	Feb. 28, 2030	Jan. 31, 2039			Jul. 30, 2015	Mar. 30, 2034
Forward Starting Interest Rate Swap Termination Date	Oct. 31, 2014