Income Taxes - Components of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Millions	Jan. 31, 2020	Jan. 31, 2019	Jan. 31, 2018
Deferred tax assets:
Losses and deductions carryforward	$ 218	$ 173
Deferred stock-based expense	193	145
Tax credits	913	605
Deferred rent expense	0	71
Accrued liabilities	214	138
Lease liabilities	769
Financing obligation	9	102
Deferred revenue	4	0
Other	22	22
Total deferred tax assets	2,342	1,256
Less valuation allowance	(290)	(205)
Deferred tax assets, net of valuation allowance	2,052	1,051
Deferred tax liabilities:
Deferred commissions	(449)	(347)
Purchased intangibles	(915)	(382)
Depreciation and amortization	(76)	(145)
Basis difference on strategic and other investments	(69)	(56)
Deferred revenue	0	(17)
Lease right-of-use assets	(695)
Total deferred tax liabilities	(2,204)	$ (947)
Net deferred tax assets (liabilities)	$ (152)
Net deferred tax assets (liabilities)			$ 104