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%