Stockholders' Equity - Schedule of Restricted Stock Activity (Detail) $ / shares in Units, shares in Millions, $ in Millions	12 Months Ended
	Jan. 31, 2020 USD ($) $ / shares shares
Restricted Stock
Restricted Stock Outstanding
Beginning balance (in shares)	21
Granted (in shares)	20
Canceled (in shares)	(2)
Vested and converted to shares (in shares)	(12)
Ending balance (in shares)	28
Expected to vest (in shares)	24
Restricted Stock Outstanding, Weighted-Average Exercise Price
Beginning balance (in dollars per share) | $ / shares	$ 103.33
Granted (in dollars per share) | $ / shares	156.21
Canceled (in dollars per share) | $ / shares	120.93
Vested and converted to shares (in dollars per share) | $ / shares	106.39
Ending balance (in dollars per share) | $ / shares	$ 140.14
Restricted Stock Outstanding, Aggregate Intrinsic Value
Aggregate Intrinsic Value, Outstanding | $	$ 5,128
Aggregate Intrinsic Value, Expected to vest | $	$ 4,452
Performance shares
Restricted Stock Outstanding
Granted (in shares)	1
Restricted Stock Outstanding, Weighted-Average Exercise Price
Granted (in dollars per share) | $ / shares	$ 161.50