Leases (Leases Cost) (Details) - USD ($) $ in Millions	12 Months Ended
Jan. 31, 2021	Jan. 31, 2020	Jan. 31, 2019
Leases [Abstract]
Operating lease cost	$ 2,626	$ 2,670
Amortization of right-of-use assets	583	480
Interest on lease obligations	298	306
Variable lease cost	$ 777	$ 691
Rentals under operating leases and short-term rental arrangements			$ 3,000

Amount of interest expense on finance lease liability.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 50
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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-Publisher FASB
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-Topic 842
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- Definition

Amount of amortization expense attributable to right-of-use asset from finance lease.

+ References

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- References

No definition available.

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- Definition

Amount of single lease cost, calculated by allocation of remaining cost of lease over remaining lease term. Includes, but is not limited to, single lease cost, after impairment of right-of-use asset, calculated by amortization of remaining right-of-use asset and accretion of lease liability.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 55
-Paragraph 53
-URI http://asc.fasb.org/extlink&oid=121568110&loc=SL77918982-209971

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-Paragraph 4
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=121609121&loc=SL77918686-209980

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- Definition

Cash payments to lessor's for use of assets under operating leases.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
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- Definition

Amount of variable lease cost, excluded from lease liability, recognized when obligation for payment is incurred for finance and operating leases.

+ References

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