Stockholders' Equity - Summary of Stock Option Activity (Detail)	9 Months Ended	12 Months Ended
	Oct. 31, 2020 USD ($) $ / shares shares	Jan. 31, 2020 USD ($) $ / shares shares
Number of shares
Options outstanding, Beginning balance (in shares) | shares	13,448,026
Options granted (in shares) | shares	1,368,632
Options exercised (in shares) | shares	(1,407,370)
Options forfeited/cancelled (in shares) | shares	(195,630)
Options outstanding, Ending balance (in shares) | shares	13,213,658	13,448,026
Options vested and exercisable (in shares) | shares	6,756,111
Options vested and exercisable and expected to vest thereafter (in shares) | shares	13,213,658
Weighted average exercise price
Options outstanding, Beginning balance (in usd per share) | $ / shares	$ 40.64
Options granted (in usd per share) | $ / shares	177.44
Options exercised (in usd per share) | $ / shares	17.91
Options forfeited/cancelled (in usd per share) | $ / shares	121.20
Options outstanding, Ending balance (in usd per share) | $ / shares	55.83	$ 40.64
Options vested and exercisable (in usd per share) | $ / shares	14.19
Options vested and exercisable and expected to vest thereafter (in usd per share) | $ / shares	$ 55.83
Weighted average remaining contractual term (in years), Options outstanding	5 years 2 months 12 days	5 years 4 months 24 days
Weighted average remaining contractual term (in years), Options vested and exercisable	3 years
Weighted average remaining contractual term (in years), Options vested and exercisable and expected to vest thereafter	5 years 2 months 12 days
Aggregate intrinsic value
Options outstanding | $	$ 2,830,945,659	$ 1,426,502,005
Options vested and exercisable | $	1,728,597,328
Options vested and exercisable and expected to vest thereafter | $	$ 2,830,945,659