Leases and Other Commitments - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Oct. 31, 2020	Oct. 31, 2019	Oct. 31, 2020	Oct. 31, 2019
Other Commitments [Line Items]
Operating lease extension term (some leases)	5 years		5 years
Operating lease termination option			1 year
Total operating lease costs	$ 278	$ 230	$ 815	$ 653
Cash payments on operating leases	222		672
Right-of use assets obtained in exchange for operating lease liabilities	$ 196		$ 562
Operating lease, weighted average remaining lease term	6 years		6 years
Operating lease, weighted average discount rate	2.50%		2.50%
Finance leases, weighted-average remaining lease term	18 years		18 years
Finance lease, weighted average discount rate	4.20%		4.20%
Sublease income, next five years	$ 175		$ 175
Sublease income, thereafter	39		39
Operating leases, not yet commenced	1,900		1,900
Operating lease commitment balance, including leases not yet commenced	5,400		5,400
Letter of credit
Other Commitments [Line Items]
Value of outstanding letters of credit	102		102
Facilities Space
Other Commitments [Line Items]
Operating lease commitment balance, including leases not yet commenced	$ 4,800		$ 4,800
Minimum
Other Commitments [Line Items]
Operating lease term	1 year		1 year
Operating lease term, not yet commenced	3 years		3 years
Maximum
Other Commitments [Line Items]
Operating lease term	22 years		22 years
Operating lease term, not yet commenced	18 years		18 years