Taxes (Schedule of Deferred Tax Balances) (Details) - USD ($) $ in Millions	Jan. 31, 2021	Jan. 31, 2020
Deferred tax assets:
Loss and tax credit carryforwards	$ 9,179	$ 9,056
Accrued liabilities	2,582	2,483
Share-based compensation	224	250
Lease obligations	4,450	4,098
Other	589	887
Total deferred tax assets	17,024	16,774
Valuation allowances	(8,782)	(8,588)
Deferred tax assets, net of valuation allowances	8,242	8,186
Deferred tax liabilities:
Property and equipment	4,802	4,364
Acquired intangibles	1,071	1,153
Inventory	1,235	1,414
Lease right of use assets	4,390	3,998
Mark-to-market investments	2,678	723
Other	675	824
Total deferred tax liabilities	14,851	12,476
Net deferred tax liabilities	$ 6,609	$ 4,290