Leases Schedule of Other Information Relating to Lease Liabilities (Details) $ in Millions	6 Months Ended
	Jul. 31, 2019 USD ($)
Leases [Abstract]
Operating cash flows from operating leases	$ 1,294
Operating cash flows from finance leases	132
Financing cash flows from finance leases	245
Assets obtained in exchange for operating lease obligations	1,119
Assets obtained in exchange for finance lease obligations	$ 319
Weighted-average remaining lease term - operating leases	15 years 8 months 12 days
Weighted-average remaining lease term - finance leases	14 years 8 months 12 days
Weighted-average discount rate - operating leases	5.30%
Weighted-average discount rate - finance leases	9.20%