Shareholders' Equity (Schedule of Share Repurchases) (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	12 Months Ended
Jan. 31, 2021	Jan. 31, 2020	Jan. 31, 2019
Equity [Abstract]
Total number of shares repurchased (in shares)	19.4	53.9	79.5
Average price paid per share (in USD per share)	$ 135.20	$ 105.98	$ 93.18
Total cash paid for share repurchases	$ 2,625	$ 5,717	$ 7,410

Equity impact of the cost of common and preferred stock that were repurchased during the period. Recorded using the cost method.

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