Stockholders' Equity - Stock Activity (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	9 Months Ended
	Oct. 31, 2018
Shares available for grant
Shares Available for Grant, Balance (in shares)	50,313
Shares Available for Grant, Options granted under all plans (in shares)	(13,637)
Shares Available for Grant, Exercised (in shares)	0
Shares Available for Grant, Expired (in shares)	(78)
Shares Available for Grant, Canceled (in shares)	988
Shares Available for Grant, Balance (in shares)	64,548
Outstanding Stock Options
Outstanding Stock Options, Balance (in shares)	21,735
Outstanding Stock Options (in shares)	13,637
Outstanding Stock Options, Exercised (in shares)	(7,445)
Outstanding Stock Options, Plan shares expired (in shares)	0
Outstanding Stock Options, Canceled (in shares)	(988)
Outstanding Stock Options, Balance (in shares)	26,939
Outstanding Stock Options, Vested or expected to vest (in shares)	25,143
Outstanding Stock Options, Exercisable (in shares)	12,481
Options Outstanding Weighted-Average Exercise Price
Weighted- Average Exercise Price, Balance (in dollars per share)	$ 65.96
Weighted- Average Exercise Price, Options (in dollars per share)	68.13
Weighted- Average Exercise Price, Exercised (in dollars per share)	44.44
Weighted- Average Exercise Price, Expired (in dollars per share)	0.00
Weighted- Average Exercise Price, Canceled (in dollars per share)	80.66
Weighted- Average Exercise Price, Balance (in dollars per share)	72.47
Weighted- Average Exercise Price, Vested or expected to vest (in dollars per share)	70.80
Weighted- Average Exercise Price, Exercisable (in dollars per share)	$ 54.28
Aggregate Intrinsic Value
Weighted- Average Exercise Price, Balance	$ 1,748
Weighted- Average Exercise Price, Vested or expected to vest	1,673
Weighted- Average Exercise Price, Exercisable	$ 1,035
Restricted stock activity
Shares available for grant
Shares Available for Grant, Restricted stock activity (in shares)	(19,369)
Outstanding Stock Options
Outstanding Stock Options (in shares)	0
Options Outstanding Weighted-Average Exercise Price
Weighted- Average Exercise Price, Options (in dollars per share)	$ 0.00
Performance-based restricted stock units
Shares available for grant
Shares Available for Grant, Restricted stock activity (in shares)	(1,911)
Outstanding Stock Options
Outstanding Stock Options (in shares)	0
Options Outstanding Weighted-Average Exercise Price
Weighted- Average Exercise Price, Options (in dollars per share)	$ 0.00
Stock grants to board and advisory board members
Shares available for grant
Shares Available for Grant, Stock grants to board and advisory board members (in shares)	(115)
Outstanding Stock Options
Outstanding Stock Options (in shares)	0
Options Outstanding Weighted-Average Exercise Price
Weighted- Average Exercise Price, Options (in dollars per share)	$ 0.00
2013 Equity Incentive Plan
Shares available for grant
Shares Available for Grant, Increase in shares authorized (in shares)	40,000
Shares Available for Grant, Balance (in shares)	64,111
Outstanding Stock Options
Outstanding Stock Options, Increase in shares authorized (in shares)	0
Options Outstanding Weighted-Average Exercise Price
Weighted- Average Exercise Price, Options (in dollars per share)	$ 0.00
Amended and Restated 2004 Employee Stock Purchase Plan
Shares available for grant
Shares Available for Grant, Increase in shares authorized (in shares)	8,357
Shares Available for Grant, Balance (in shares)	5,743
Outstanding Stock Options
Outstanding Stock Options, Increase in shares authorized (in shares)	0
Options Outstanding Weighted-Average Exercise Price
Weighted- Average Exercise Price, Options (in dollars per share)	$ 0.00