Stockholders' Equity - Stock Options Outstanding (Detail) $ / shares in Units, shares in Millions, $ in Millions	12 Months Ended
	Jan. 31, 2020 USD ($) $ / shares shares
Shares Available for Grant
Beginning balance (in shares) | shares	64
Ending balance (in shares) | shares	77
Outstanding Stock Options
Beginning balance (in shares) | shares	26
Options granted under all plans (in shares) | shares	10
Exercised (in shares) | shares	(7)
Plan shares expired or canceled (in shares) | shares	(2)
Ending balance (in shares) | shares	27
Outstanding Stock Options, Vested or expected to vest (in shares) | shares	25
Outstanding Stock Options, Exercisable (in shares) | shares	14
Options Outstanding Weighted-Average Exercise Price
Beginning balance (in dollars per share)	$ 74.15
Options granted under all plans (in dollars per share)	132.72
Exercised (in dollars per share)	55.67
Plan shares expired or canceled (in dollars per share)	116.84
Ending balance (in dollars per share)	98.56
Weighted-Average Exercise Price, Vested or expected to vest (in dollars per share)	95.80
Weighted-Average Exercise Price, Exercisable (in dollars per share)	$ 66.34
Aggregate Intrinsic Value
Balance | $	$ 2,222
Vested or expected to vest | $	2,155
Exercisable | $	$ 1,589
Stock Options Outstanding Information
Options, Number Outstanding (in shares) | shares	27
Weighted-Average Remaining Contractual Life, Options Outstanding	4 years 6 months
Weighted-Average Exercise Price, Options Outstanding (in dollars per share)	$ 98.56
Options Exercisable, Number of Shares (in shares) | shares	14
Options Exercisable, Weighted-Average Exercise Price (in dollars per share)	$ 66.34
Restricted Stock
Shares Available for Grant
Restricted stock and restricted stock unit activity (in shares) | shares	(28)
Performance shares
Shares Available for Grant
Restricted stock and restricted stock unit activity (in shares) | shares	(2)
2013 Equity Incentive Plan
Shares Available for Grant
Increase in shares authorized (in shares) | shares	36
Ending balance (in shares) | shares	74
2014 Inducement Plan
Shares Available for Grant
Increase in shares authorized (in shares) | shares	2
Ending balance (in shares) | shares	2
Acquired equity plans
Shares Available for Grant
Increase in shares authorized (in shares) | shares	13
Ending balance (in shares) | shares	1
$0.36 to $52.30
Stock Options Outstanding Information
Range of Exercise Prices, Minimum (in dollars per share)	$ 0.36
Range of Exercise Prices, Maximum (in dollars per share)	$ 52.30
Options, Number Outstanding (in shares) | shares	5
Weighted-Average Remaining Contractual Life, Options Outstanding	3 years 8 months 12 days
Weighted-Average Exercise Price, Options Outstanding (in dollars per share)	$ 29.10
Options Exercisable, Number of Shares (in shares) | shares	4
Options Exercisable, Weighted-Average Exercise Price (in dollars per share)	$ 30.55
$54.36 to $75.57
Stock Options Outstanding Information
Range of Exercise Prices, Minimum (in dollars per share)	54.36
Range of Exercise Prices, Maximum (in dollars per share)	$ 75.57
Options, Number Outstanding (in shares) | shares	6
Weighted-Average Remaining Contractual Life, Options Outstanding	3 years
Weighted-Average Exercise Price, Options Outstanding (in dollars per share)	$ 67.41
Options Exercisable, Number of Shares (in shares) | shares	5
Options Exercisable, Weighted-Average Exercise Price (in dollars per share)	$ 66.08
$76.48 to $113.00
Stock Options Outstanding Information
Range of Exercise Prices, Minimum (in dollars per share)	76.48
Range of Exercise Prices, Maximum (in dollars per share)	$ 113.00
Options, Number Outstanding (in shares) | shares	3
Weighted-Average Remaining Contractual Life, Options Outstanding	3 years 4 months 24 days
Weighted-Average Exercise Price, Options Outstanding (in dollars per share)	$ 83.71
Options Exercisable, Number of Shares (in shares) | shares	3
Options Exercisable, Weighted-Average Exercise Price (in dollars per share)	$ 82.59
$118.04
Stock Options Outstanding Information
Range of Exercise Prices, Minimum (in dollars per share)	118.04
Range of Exercise Prices, Maximum (in dollars per share)	$ 118.04
Options, Number Outstanding (in shares) | shares	4
Weighted-Average Remaining Contractual Life, Options Outstanding	5 years 1 month 6 days
Weighted-Average Exercise Price, Options Outstanding (in dollars per share)	$ 118.04
Options Exercisable, Number of Shares (in shares) | shares	2
Options Exercisable, Weighted-Average Exercise Price (in dollars per share)	$ 118.04
$122.03 to $158.76
Stock Options Outstanding Information
Range of Exercise Prices, Minimum (in dollars per share)	122.03
Range of Exercise Prices, Maximum (in dollars per share)	$ 158.76
Options, Number Outstanding (in shares) | shares	3
Weighted-Average Remaining Contractual Life, Options Outstanding	6 years 3 months 18 days
Weighted-Average Exercise Price, Options Outstanding (in dollars per share)	$ 145.38
Options Exercisable, Number of Shares (in shares) | shares	0
Options Exercisable, Weighted-Average Exercise Price (in dollars per share)	$ 133.49
$161.50
Stock Options Outstanding Information
Range of Exercise Prices, Minimum (in dollars per share)	161.50
Range of Exercise Prices, Maximum (in dollars per share)	$ 161.50
Options, Number Outstanding (in shares) | shares	6
Weighted-Average Remaining Contractual Life, Options Outstanding	6 years 1 month 6 days
Weighted-Average Exercise Price, Options Outstanding (in dollars per share)	$ 161.50
Options Exercisable, Number of Shares (in shares) | shares	0
Options Exercisable, Weighted-Average Exercise Price (in dollars per share)	$ 0.00