Commitments (Aggregate Minimum Annual Rentals Under Non-Cancelable Leases) (Details) $ in Millions	Jan. 31, 2018 USD ($)
Commitments Disclosure [Abstract]
Operating leases, future minimum payments due, next twelve months	$ 1,933
Capital leases, future minimum payments due, next twelve months	1,039
Operating leases, future minimum payments, due in two years	1,718
Capital leases, future minimum payments due in two years	987
Operating leases, future minimum payments, due in three years	1,532
Capital leases, future minimum payments due in three years	942
Operating leases, future minimum payments, due in four years	1,381
Capital leases, future minimum payments due in four years	843
Operating leases, future minimum payments, due in five years	1,158
Capital leases, future minimum payments due in five years	696
Operating leases, future minimum payments, due thereafter	7,644
Capital leases, future minimum payments due thereafter	5,423
Operating leases, future minimum payments due	15,366
Capital leases, future minimum payments due	9,930
Capital leases, future minimum payments, executory costs	27
Capital leases, future minimum payments, present value of net minimum payments	9,903
Noncash gain on future termination of financing obligation	1,111
Capital leases, future minimum payments, interest included in payments	(3,567)
Present value of minimum lease payments	$ 7,447