Investments - Schedule of Marketable Securities (Detail) - USD ($) $ in Millions	Jul. 31, 2020	Jan. 31, 2020
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 5,188	$ 3,789
Unrealized Gains	46	14
Unrealized Losses	(3)	(1)
Fair Value	5,231	3,802
Corporate notes and obligations
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	2,937	2,199
Unrealized Gains	24	9
Unrealized Losses	(2)	(1)
Fair Value	2,959	2,207
U.S. treasury securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	157	182
Unrealized Gains	3	1
Unrealized Losses	0	0
Fair Value	160	183
Mortgage backed obligations
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	313	225
Unrealized Gains	6	1
Unrealized Losses	0	0
Fair Value	319	226
Asset backed securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	1,053	779
Unrealized Gains	9	2
Unrealized Losses	(1)	0
Fair Value	1,061	781
Municipal securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	296	157
Unrealized Gains	1	1
Unrealized Losses	0	0
Fair Value	297	158
Foreign government obligations
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	107	69
Unrealized Gains	0	0
Unrealized Losses	0	0
Fair Value	107	69
U.S. agency obligations
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	17	12
Unrealized Gains	0	0
Unrealized Losses	0	0
Fair Value	17	12
Time deposits
Debt Securities, Available-for-sale [Line Items]
Amortized Cost		1
Unrealized Gains		0
Unrealized Losses		0
Fair Value		1
Covered bonds
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	308	165
Unrealized Gains	3	0
Unrealized Losses	0	0
Fair Value	$ 311	$ 165

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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