Commitments (Aggregate Minimum Annual Rentals Under Non-Cancelable Leases) (Details) $ in Millions	Jan. 31, 2019 USD ($)
Commitments Disclosure [Abstract]
Operating leases, future minimum payments due, next twelve months	$ 1,856
Capital leases, future minimum payments due, next twelve months	917
Operating leases, future minimum payments, due in two years	1,655
Capital leases, future minimum payments due in two years	856
Operating leases, future minimum payments, due in three years	1,420
Capital leases, future minimum payments due in three years	794
Operating leases, future minimum payments, due in four years	1,233
Capital leases, future minimum payments due in four years	667
Operating leases, future minimum payments, due in five years	1,063
Capital leases, future minimum payments due in five years	593
Operating leases, future minimum payments, due thereafter	6,891
Capital leases, future minimum payments due thereafter	6,069
Operating leases, future minimum payments due	14,118
Capital leases, future minimum payments due	9,896
Capital leases, future minimum payments, executory costs	23
Capital leases, future minimum payments, present value of net minimum payments	9,873
Financing obligation noncash gains and other	2,278
Capital leases, future minimum payments, interest included in payments	(4,739)
Present value of minimum lease payments	$ 7,412