Derivative Financial Instruments (Narrative) (Details) $ in Millions, ¥ in Billions, £ in Billions |
3 Months Ended | |||||
|---|---|---|---|---|---|---|
|
Apr. 30, 2019
JPY (¥)
|
Apr. 30, 2019
GBP (£)
|
Jan. 31, 2019
JPY (¥)
|
Jan. 31, 2019
GBP (£)
|
Apr. 30, 2019
USD ($)
|
Jan. 31, 2019
USD ($)
|
|
| Derivative [Line Items] | ||||||
| Cash collateral held from counterparties | $ 209 | $ 220 | ||||
| Threshold of derivative liability position requiring cash collateral | $ 150 | |||||
| Designated as hedging instrument | Net investment hedging | Japan | ||||||
| Derivative [Line Items] | ||||||
| Notional amount of nonderivative instruments | ¥ | ¥ 180 | ¥ 180 | ||||
| Designated as hedging instrument | Net investment hedging | United Kingdom | ||||||
| Derivative [Line Items] | ||||||
| Notional amount of nonderivative instruments | £ | £ 1.7 | £ 1.7 | ||||