Income Taxes - Effective Income Tax Rate Reconciliation (Details) - USD ($) $ in Millions		12 Months Ended
		Jan. 31, 2020	Jan. 31, 2019	Jan. 31, 2018
Income Tax Disclosure [Abstract]
U.S. federal taxes at statutory rate		$ 148	$ 206	$ 142
State, net of the federal benefit		40	79	(21)
Effects of non-U.S. operations		540	379	(35)
Tax credits		(195)	(132)	(107)
Non-deductible expenses		119	63	53
Excess tax benefits related to shared based compensation		(166)	(137)	(135)
Effect of U.S. tax law change		6	43	126
Change in valuation allowance		85	(612)	42
Other, net		3	(16)	(5)
Provision for (benefit from) income taxes	[1]	$ 580	$ (127)	$ 60
Statutory tax rate		21.00%	21.00%	33.80%

[1] Amounts include a benefit related to the partial release of the valuation allowance of $612 million, and $2 million, for fiscal 2019 and 2018, respectively. The fiscal 2019 benefit was partially offset by an increase in unrecognized tax benefits.