Leases Schedule of Other Information Relating to Lease Liabilities (Details) $ in Millions |
3 Months Ended |
|---|---|
|
Apr. 30, 2019
USD ($)
| |
| Leases [Abstract] | |
| Operating cash flows from operating leases | $ 639 |
| Operating cash flows from finance leases | 49 |
| Financing cash flows from finance leases | 134 |
| Assets obtained in exchange for operating lease obligations | 189 |
| Assets obtained in exchange for finance lease obligations | $ 95 |
| Weighted-average remaining lease term - operating leases | 15 years 9 months 18 days |
| Weighted-average remaining lease term - finance leases | 14 years 4 months 24 days |
| Weighted-average discount rate - operating leases | 5.30% |
| Weighted-average discount rate - finance leases | 9.50% |