Derivative Financial Instruments (Narrative) (Details) $ in Millions, ¥ in Billions, £ in Billions	9 Months Ended		12 Months Ended
	Oct. 31, 2015 JPY (¥)	Oct. 31, 2015 GBP (£)	Jan. 31, 2015 JPY (¥)	Jan. 31, 2015 GBP (£)	Oct. 31, 2015 USD ($)	Jan. 31, 2015 USD ($)
Derivative [Line Items]
Cash collateral held from counterparties | $					$ 341	$ 323
Threshold of derivative liability position requiring cash collateral | $					$ 150
Net investment hedging | United Kingdom
Derivative [Line Items]
Notional amount of nonderivative instruments				£ 2.5
Designated as hedging instrument | Net investment hedging | United Kingdom
Derivative [Line Items]
Notional amount of nonderivative instruments		£ 2.5
Designated as hedging instrument | Net investment hedging | Japan
Derivative [Line Items]
Notional amount of nonderivative instruments | ¥	¥ 10		¥ 100