Investments - Schedule of Marketable Securities (Detail) - USD ($) $ in Millions	Oct. 31, 2018	Jan. 31, 2018
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 1,363	$ 1,991
Unrealized Gains	0	1
Unrealized Losses	(18)	(14)
Fair Value	1,345	1,978
Corporate notes and obligations
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	809	1,223
Unrealized Gains	0	1
Unrealized Losses	(10)	(7)
Fair Value	799	1,217
U.S. treasury securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	90	196
Unrealized Gains	0	0
Unrealized Losses	(2)	(2)
Fair Value	88	194
Mortgage backed obligations
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	86	100
Unrealized Gains	0	0
Unrealized Losses	(1)	(1)
Fair Value	85	99
Asset backed securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	190	251
Unrealized Gains	0	0
Unrealized Losses	(2)	(1)
Fair Value	188	250
Municipal securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	76	53
Unrealized Gains	0	0
Unrealized Losses	(1)	(1)
Fair Value	75	52
Foreign government obligations
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	51	87
Unrealized Gains	0	0
Unrealized Losses	(1)	(1)
Fair Value	50	86
U.S. agency obligations
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	4	19
Unrealized Gains	0	0
Unrealized Losses	0	0
Fair Value	4	19
Commercial paper
Debt Securities, Available-for-sale [Line Items]
Amortized Cost		11
Unrealized Gains		0
Unrealized Losses		0
Fair Value		11
Covered bonds
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	57	51
Unrealized Gains	0	0
Unrealized Losses	(1)	(1)
Fair Value	$ 56	$ 50

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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Amount, before tax, of unrealized loss 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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Amount of 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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