Short-term Borrowings and Long-term Debt (Narrative) (Details) - USD ($)	12 Months Ended
Jan. 31, 2022	Jan. 31, 2021	Jan. 31, 2020
Debt Instrument [Line Items]
Short-term borrowings	$ 410,000,000	$ 224,000,000
Average interest rate	2.90%	1.90%
Letters of credit, drawn	$ 1,700,000,000	$ 1,800,000,000
Loss on extinguishment of debt	2,410,000,000	0	$ 0
Premiums paid to extinguish debt	2,317,000,000	0	0
Proceeds from issuance of long-term debt	6,945,000,000	0	$ 5,492,000,000
Unsecured debt [Member]
Debt Instrument [Line Items]
Proceeds from issuance of long-term debt	$ 0
Fronted and Syndicated Lines of Credit [Member] \| [Minimum]
Debt Instrument [Line Items]
Commitment fee	0.00015
Fronted and Syndicated Lines of Credit [Member] \| [Maximum]
Debt Instrument [Line Items]
Commitment fee	0.00040
Fronted and Syndicated Lines of Credit [Member] \| London Interbank Offered Rate (LIBOR) [Member] \| [Minimum]
Debt Instrument [Line Items]
Variable rate commitment	0.0050
Letter of Credit [Member]
Debt Instrument [Line Items]
Principal Amount	$ 1,800,000,000	$ 1,800,000,000

Face (par) amount of debt instrument at time of issuance.

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