Stockholders' Equity - Stock Options Outstanding (Detail) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Apr. 30, 2019 USD ($) $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options, Number Outstanding (in shares) | shares	29
Weighted- Average Remaining Contractual Life (Years), Options Outstanding	5 years
Weighted- Average Exercise Price, Options Outstanding (in dollars per share)	$ 92.92
Options Exercisable, Number of Shares (in shares) | shares	13
Options Exercisable, Weighted- Average Exercise Price (in dollars per share)	$ 63.88
Outstanding Stock Options
Outstanding Stock Options, Balance (in shares) | shares	26
Options granted under all plans (in shares) | shares	5
Outstanding Stock Options, Exercised (in shares) | shares	(2)
Outstanding Stock Options, Balance (in shares) | shares	29
Outstanding Stock Options, Vested or expected to vest (in shares) | shares	27
Outstanding Stock Options, Exercisable (in shares) | shares	13
Options Outstanding Weighted-Average Exercise Price
Weighted- Average Exercise Price, Balance (in dollars per share)	$ 74.15
Weighted- Average Exercise Price, Options granted under all plans (in dollars per share)	161.44
Weighted- Average Exercise Price, Exercised (in dollars per share)	52.47
Weighted- Average Exercise Price, Balance (in dollars per share)	92.92
Weighted- Average Exercise Price, Vested or expected to vest (in dollars per share)	89.62
Weighted- Average Exercise Price, Exercisable (in dollars per share)	$ 63.88
Aggregate Intrinsic Value
Weighted- Average Exercise Price, Balance | $	$ 2,126
Weighted- Average Exercise Price, Vested or expected to vest | $	2,046
Weighted- Average Exercise Price, Exercisable | $	$ 1,354
$0.27 to $52.30
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Range of Exercise Prices, Minimum (in dollars per share)	$ 0.03
Range of Exercise Prices, Maximum (in dollars per share)	$ 21.54
Options, Number Outstanding (in shares) | shares	5
Weighted- Average Remaining Contractual Life (Years), Options Outstanding	4 years 6 months
Weighted- Average Exercise Price, Options Outstanding (in dollars per share)	$ 29.30
Options Exercisable, Number of Shares (in shares) | shares	4
Options Exercisable, Weighted- Average Exercise Price (in dollars per share)	$ 32.78
$54.36 to $75.57
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Range of Exercise Prices, Minimum (in dollars per share)	22.12
Range of Exercise Prices, Maximum (in dollars per share)	$ 59.34
Options, Number Outstanding (in shares) | shares	8
Weighted- Average Remaining Contractual Life (Years), Options Outstanding	3 years 9 months 18 days
Weighted- Average Exercise Price, Options Outstanding (in dollars per share)	$ 67.92
Options Exercisable, Number of Shares (in shares) | shares	5
Options Exercisable, Weighted- Average Exercise Price (in dollars per share)	$ 65.34
$76.48 to $113.00
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Range of Exercise Prices, Minimum (in dollars per share)	59.37
Range of Exercise Prices, Maximum (in dollars per share)	$ 75.01
Options, Number Outstanding (in shares) | shares	4
Weighted- Average Remaining Contractual Life (Years), Options Outstanding	4 years
Weighted- Average Exercise Price, Options Outstanding (in dollars per share)	$ 84.47
Options Exercisable, Number of Shares (in shares) | shares	3
Options Exercisable, Weighted- Average Exercise Price (in dollars per share)	$ 82.67
$118.04
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Range of Exercise Prices, Minimum (in dollars per share)	75.57
Range of Exercise Prices, Maximum (in dollars per share)	$ 75.57
Options, Number Outstanding (in shares) | shares	5
Weighted- Average Remaining Contractual Life (Years), Options Outstanding	5 years 10 months 24 days
Weighted- Average Exercise Price, Options Outstanding (in dollars per share)	$ 118.04
Options Exercisable, Number of Shares (in shares) | shares	1
Options Exercisable, Weighted- Average Exercise Price (in dollars per share)	$ 118.04
$122.03 to $158.76
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Range of Exercise Prices, Minimum (in dollars per share)	76.48
Range of Exercise Prices, Maximum (in dollars per share)	$ 82.08
Options, Number Outstanding (in shares) | shares	1
Weighted- Average Remaining Contractual Life (Years), Options Outstanding	6 years 3 months 18 days
Weighted- Average Exercise Price, Options Outstanding (in dollars per share)	$ 135.29
Options Exercisable, Number of Shares (in shares) | shares	0
Options Exercisable, Weighted- Average Exercise Price (in dollars per share)	$ 0.00
$161.50
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Range of Exercise Prices, Minimum (in dollars per share)	82.55
Range of Exercise Prices, Maximum (in dollars per share)	$ 113.00
Options, Number Outstanding (in shares) | shares	6
Weighted- Average Remaining Contractual Life (Years), Options Outstanding	6 years 10 months 24 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