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Shareholders' Equity (Narrative) (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	12 Months Ended
	Jan. 31, 2021	Jan. 31, 2020	Jan. 31, 2019	Feb. 18, 2021	Feb. 01, 2018	Oct. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock, par (in USD per share)	$ 0.10	$ 0.10
Common stock, shares authorized (in shares)	11,000	11,000
Share-based compensation expense	$ 1,169	$ 854	$ 773
Tax benefit	$ 300	$ 200	200
Compensation awards (in shares)					260
Common Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares, issued (in shares)	2,800	2,800
Shares, outstanding (in shares)	2,800	2,800
2017 Share Repurchase Program [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Repurchase program						$ 20,000
Repurchase amount	$ 3,000
2021 Share Repurchase Program [Member] \| Subsequent Event [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Repurchase program				$ 20,000
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense	$ 742	$ 553	$ 456
Expected dividend rate	4.40%	4.90%	7.20%
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected dividend rate	4.50%	5.10%	6.20%
Restricted Stock And Performance Share Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense	$ 277	$ 270	$ 293
Annual [Member] \| Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting rights, percentage		25.00%
Vesting period		4 years
Three Years from Grant Date [Member] \| Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting rights, percentage			50.00%
Five Years from Grant Date [Member] \| Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting rights, percentage			50.00%
Minimum \| Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period			3 years
Minimum \| Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting rights, percentage	0.00%
Minimum \| Restricted Stock And Performance Share Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	1 year
Maximum \| Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period			5 years
Maximum \| Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting rights, percentage	150.00%
Maximum \| Restricted Stock And Performance Share Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	3 years