Stockholders' Equity - Schedule of Restricted Stock Activity (Details) $ / shares in Units, shares in Millions, $ in Millions	9 Months Ended
	Oct. 31, 2020 USD ($) $ / shares shares
Restricted Stock
Restricted Stock Outstanding
Beginning balance (in shares)	28
Granted (in shares)	11
Canceled (in shares)	(2)
Vested and converted to shares (in shares)	(10)
Ending balance (in shares)	28
Expected to vest (in shares)	25
Restricted Stock Outstanding, Weighted-Average Exercise Price
Beginning balance (in dollars per share) | $ / shares	$ 140.14
Granted (in dollars per share) | $ / shares	163.01
Canceled (in dollars per share) | $ / shares	142.18
Vested and converted to shares (in dollars per share) | $ / shares	131.96
Ending balance (in dollars per share) | $ / shares	$ 152.31
Restricted Stock Outstanding, Aggregate Intrinsic Value
Aggregate Intrinsic Value, Outstanding | $	$ 6,553
Aggregate Intrinsic Value, Expected to vest | $	$ 5,725
Performance shares
Restricted Stock Outstanding
Granted (in shares)	1
Restricted Stock Outstanding, Weighted-Average Exercise Price
Granted (in dollars per share) | $ / shares	$ 154.14