Stockholders' Equity - Stock Options Outstanding (Details) $ / shares in Units, shares in Millions, $ in Millions	9 Months Ended
	Oct. 31, 2020 USD ($) $ / shares shares
Outstanding Stock Options
Beginning balance (in shares) | shares	27
Options granted under all plans (in shares) | shares	8
Exercised (in shares) | shares	(10)
Plan shares expired or canceled (in shares) | shares	(1)
Ending balance (in shares) | shares	24
Outstanding Stock Options, Vested or expected to vest (in shares) | shares	22
Outstanding Stock Options, Exercisable (in shares) | shares	10
Options Outstanding Weighted-Average Exercise Price
Beginning balance (in dollars per share)	$ 98.56
Options granted under all plans (in dollars per share)	145.30
Exercised (in dollars per share)	79.77
Plan shares expired or canceled (in dollars per share)	133.43
Ending balance (in dollars per share)	118.31
Weighted-Average Exercise Price, Vested or expected to vest (in dollars per share)	115.96
Weighted-Average Exercise Price, Exercisable (in dollars per share)	$ 82.86
Aggregate Intrinsic Value
Balance | $	$ 2,765
Vested or expected to vest | $	2,611
Exercisable | $	$ 1,523
Stock Options Outstanding Information
Range of Exercise Prices, Maximum (in dollars per share)	$ 154.14
Options, Number Outstanding (in shares) | shares	24
Weighted- Average Remaining Contractual Life (Years)	4 years 10 months 24 days
Weighted-Average Exercise Price, Options Outstanding (in dollars per share)	$ 118.31
Options Exercisable, Number of Shares (in shares) | shares	10
Options Exercisable, Weighted-Average Exercise Price (in dollars per share)	$ 82.86
$0.36 to $59.34
Stock Options Outstanding Information
Range of Exercise Prices, Minimum (in dollars per share)	0.36
Range of Exercise Prices, Maximum (in dollars per share)	$ 59.34
Options, Number Outstanding (in shares) | shares	5
Weighted- Average Remaining Contractual Life (Years)	3 years 3 months 18 days
Weighted-Average Exercise Price, Options Outstanding (in dollars per share)	$ 39.88
Options Exercisable, Number of Shares (in shares) | shares	4
Options Exercisable, Weighted-Average Exercise Price (in dollars per share)	$ 41.36
$59.64 to $98.90
Stock Options Outstanding Information
Range of Exercise Prices, Minimum (in dollars per share)	59.64
Range of Exercise Prices, Maximum (in dollars per share)	$ 98.90
Options, Number Outstanding (in shares) | shares	3
Weighted- Average Remaining Contractual Life (Years)	3 years 2 months 12 days
Weighted-Average Exercise Price, Options Outstanding (in dollars per share)	$ 78.09
Options Exercisable, Number of Shares (in shares) | shares	3
Options Exercisable, Weighted-Average Exercise Price (in dollars per share)	$ 78.28
$106.83 to $125.44
Stock Options Outstanding Information
Range of Exercise Prices, Minimum (in dollars per share)	106.83
Range of Exercise Prices, Maximum (in dollars per share)	$ 125.44
Options, Number Outstanding (in shares) | shares	3
Weighted- Average Remaining Contractual Life (Years)	4 years 4 months 24 days
Weighted-Average Exercise Price, Options Outstanding (in dollars per share)	$ 118.49
Options Exercisable, Number of Shares (in shares) | shares	2
Options Exercisable, Weighted-Average Exercise Price (in dollars per share)	$ 118.52
$142.33 to $148.95
Stock Options Outstanding Information
Range of Exercise Prices, Minimum (in dollars per share)	142.33
Range of Exercise Prices, Maximum (in dollars per share)	$ 148.95
Options, Number Outstanding (in shares) | shares	2
Weighted- Average Remaining Contractual Life (Years)	5 years 8 months 12 days
Weighted-Average Exercise Price, Options Outstanding (in dollars per share)	$ 146.82
Options Exercisable, Number of Shares (in shares) | shares	0
Options Exercisable, Weighted-Average Exercise Price (in dollars per share)	$ 146.43
$154.14
Stock Options Outstanding Information
Range of Exercise Prices, Minimum (in dollars per share)	$ 154.14
Options, Number Outstanding (in shares) | shares	6
Weighted- Average Remaining Contractual Life (Years)	6 years 6 months
Weighted-Average Exercise Price, Options Outstanding (in dollars per share)	$ 154.14
Options Exercisable, Number of Shares (in shares) | shares	0
Options Exercisable, Weighted-Average Exercise Price (in dollars per share)	$ 0.00
$155.20 to $249.67
Stock Options Outstanding Information
Range of Exercise Prices, Minimum (in dollars per share)	155.20
Range of Exercise Prices, Maximum (in dollars per share)	$ 249.67
Options, Number Outstanding (in shares) | shares	5
Weighted- Average Remaining Contractual Life (Years)	5 years 6 months
Weighted-Average Exercise Price, Options Outstanding (in dollars per share)	$ 165.84
Options Exercisable, Number of Shares (in shares) | shares	1
Options Exercisable, Weighted-Average Exercise Price (in dollars per share)	$ 161.50