Leases (Schedule of Other Information Relating to Lease Liabilities) (Details) - USD ($) $ in Millions	12 Months Ended
	Jan. 31, 2021	Jan. 31, 2020
Leases [Abstract]
Operating cash flows from operating leases	$ 2,629	$ 2,614
Operating cash flows from finance leases	286	278
Financing cash flows from finance leases	546	485
Assets obtained in exchange for operating lease obligations	2,131	2,151
Assets obtained in exchange for finance lease obligations	$ 1,547	$ 1,081
Weighted-average remaining lease term - operating leases	12 years 6 months	15 years 7 months 6 days
Weighted-average remaining lease term - finance leases	13 years 8 months 12 days	14 years 4 months 24 days
Weighted-average discount rate - operating leases	6.10%	5.40%
Weighted-average discount rate - finance leases	6.80%	8.60%