Fair Value Measurements Investment in JD (Details) - JD.com [Member] - USD ($) $ in Millions |
Apr. 30, 2019 |
Jan. 31, 2019 |
|---|---|---|
| Investment in JD [Line Items] | ||
| Equity Securities, FV-NI | $ 4,366 | $ 3,583 |
| Inputs, Level 1 [Member] | ||
| Investment in JD [Line Items] | ||
| Equity Securities, FV-NI | 2,181 | 1,791 |
| Inputs, Level 2 [Member] | ||
| Investment in JD [Line Items] | ||
| Equity Securities, FV-NI | $ 2,185 | $ 1,792 |