Investments - Schedule of Marketable Securities (Detail) - USD ($) $ in Millions	Jan. 31, 2020	Jan. 31, 2019
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 3,789	$ 1,685
Unrealized Gains	14	0
Unrealized Losses	(1)	(12)
Fair Value	3,802	1,673
Corporate notes and obligations
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	2,199	1,027
Unrealized Gains	9	0
Unrealized Losses	(1)	(8)
Fair Value	2,207	1,019
U.S. treasury securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	182	89
Unrealized Gains	1	0
Unrealized Losses	0	(1)
Fair Value	183	88
Mortgage backed obligations
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	225	79
Unrealized Gains	1	0
Unrealized Losses	0	(1)
Fair Value	226	78
Asset backed securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	779	245
Unrealized Gains	2	0
Unrealized Losses	0	(1)
Fair Value	781	244
Municipal securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	157	104
Unrealized Gains	1	0
Unrealized Losses	0	0
Fair Value	158	104
Foreign government obligations
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	69	58
Unrealized Gains	0	0
Unrealized Losses	0	(1)
Fair Value	69	57
U.S. agency obligations
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	12	4
Unrealized Gains	0	0
Unrealized Losses	0	0
Fair Value	12	4
Time deposits
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	1	4
Unrealized Gains	0	0
Unrealized Losses	0	0
Fair Value	1	4
Covered bonds
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	165	75
Unrealized Gains	0	0
Unrealized Losses	0	0
Fair Value	$ 165	$ 75

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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