Income Taxes (Details) - USD ($) $ in Millions		3 Months Ended			9 Months Ended
		Oct. 31, 2020	Jul. 31, 2020	Oct. 31, 2019	Oct. 31, 2020	Oct. 31, 2019
Income Tax Disclosure [Abstract]
Benefit from (provision for) income taxes	[1]	$ (169)		$ (173)	$ 1,669	$ (336)
Pretax income		1,250		$ 64	$ 2,136	$ 710
Effective tax rate					(78.00%)	47.00%
Discrete tax benefit			$ 2,000
Reasonably possible decrease of unrecognized tax benefits		$ 6			$ 6

[1] In the second quarter of fiscal 2021, the Company recorded approximately $2.0 billion of benefit from income taxes due to a one-time discrete tax item from the recognition of deferred tax assets related to an intra-entity transfer of intangible property.