Short-term Borrowings and Long-term Debt (Schedule of Long-term Debt Instruments) (Details) - USD ($) $ in Millions	3 Months Ended
	Apr. 30, 2020	Apr. 30, 2019
Long-term debt due within one year
Balances as of February 1, 2020	$ 5,362
Proceeds from issuance of long-term debt	0
Repayments of long-term debt	0
Reclassifications of long-term debt	622
Other	(1)
Balances as of April 30, 2020	5,983	$ 1,464
Long-term debt
Balances as of February 1, 2020	43,714
Repayments of long-term debt	0
Reclassifications of long-term debt	(622)
Other	(86)
Balances as of April 30, 2020	43,006	47,425
Total
Balances as of February 1, 2020	49,076
Proceeds from issuance of long-term debt	0	$ 3,978
Repayments of long-term debt	0
Reclassifications of long-term debt	0
Other	(87)
Balances as of April 30, 2020	$ 48,989