Derivative Financial Instruments (Narrative) (Details)		3 Months Ended								3 Months Ended
	Apr. 30, 2014 USD ($)	Apr. 30, 2014 Cash Flow Hedging [Member] USD ($)	Apr. 30, 2014 Fair Value Hedging [Member]	Apr. 30, 2014 Net Investment Hedging [Member]	Apr. 30, 2014 Net Investment Hedging [Member] United Kingdom and Japan [Member]	Apr. 30, 2014 Net Investment Hedging [Member] United Kingdom [Member] GBP (£)	Jan. 31, 2014 Net Investment Hedging [Member] United Kingdom [Member] GBP (£)	Apr. 30, 2014 Net Investment Hedging [Member] JAPAN JPY (¥)	Jan. 31, 2014 Net Investment Hedging [Member] JAPAN JPY (¥)	Apr. 30, 2014 Cash Flow Hedging [Member] Interest Rate Swap [Member]	Apr. 30, 2014 Cash Flow Hedging [Member] Cross Currency Interest Rate Contract [Member]	Apr. 30, 2014 Netting and Collateral [Member] USD ($)	Jan. 31, 2014 Netting and Collateral [Member] USD ($)
Derivative [Line Items]
Derivative, Collateral, Obligation to Return Cash												$ 511,000,000	$ 641,000,000
Threshold of derivative liability position requiring cash collateral	150,000,000
Investment Maturity Date			May 31, 2014
Investment maturity date range start				Oct. 30, 2023	Aug. 31, 2014					Aug. 31, 2014	Apr. 30, 2022
Investment maturity date range end				Feb. 28, 2030	Jan. 31, 2039					Jul. 30, 2015	Mar. 30, 2034
Debt designated as United Kingdom net investment hedge						2,500,000,000	2,500,000,000
Debt designated as Japanese net investment hedge								200,000,000,000	200,000,000,000
Notional Amount		2,000,000,000
Deferred (Gain) Loss on Discontinuation of Cash Flow Hedge		$ 107,000,000