Leases and Other Commitments - Components of Lease Expense and Supplemental Cash Flow Information (Details) $ in Millions	12 Months Ended
	Jan. 31, 2020 USD ($)
Commitments and Contingencies Disclosure [Abstract]
Operating lease cost	$ 913
Finance lease cost:
Amortization of right-of-use assets	65
Interest on lease liabilities	20
Total finance lease cost	85
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash outflows for operating leases	827
Operating cash outflows for finance leases	15
Financing cash outflows for finance leases	164
Right-of-use assets obtained in exchange for lease obligations:
Operating leases	$ 509