Stockholders' Equity (Tables)

6 Months Ended

Jul. 31, 2017

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Summary of Stock Option Activity

A summary of stock option activity for the six months ended July 31, 2017 is as follows:

						Weighted
				Weighted		average
				average		remaining		Aggregate
	Number			exercise		contractual		intrinsic
	of shares			price		term (in years)		value
Options outstanding at January 31, 2017		16,282,343		$	7.48		6.3	$	567,491,532
Options granted		13,000			57.37
Options exercised		(1,918,647	)		7.06
Options forfeited/cancelled		(108,201	)		21.87
Options outstanding at July 31, 2017		14,268,495		$	7.47		5.8	$	803,181,095
Options vested and exercisable at July 31, 2017		5,648,977		$	5.19		5.3	$	330,863,470
Options vested and exercisable at July 31, 2017 and expected to vest    thereafter		14,268,495		$	7.47		5.8	$	803,181,095

Summary of Restricted Stock Unit (RSU) Activity

A summary of restricted stock unit (RSU) activity for the six months ended July 31, 2017 is as follows:

				Weighted
	Unreleased			average
	restricted			grant date
	stock units			fair value
Balance at January 31, 2017		3,362,650		$	29.33
RSUs granted		876,244			51.96
RSUs vested		(605,180	)		29.73
RSUs forfeited/cancelled		(246,247	)		30.71
Balance at July 31, 2017		3,387,467		$	35.03

Schedule of Weighted-Average Assumptions Used to Estimate Grant Date Fair Value of Options Granted

The following table presents the weighted-average assumptions used to estimate the grant date fair value of options granted during the periods presented:

	Three Months Ended July 31,			Six Months Ended July 31,
	2017		2016	2017		2016
Volatility		43%	—	43% – 44%		45% – 46%
Expected term (in years)		6.35	—		6.35	6.31 – 7.56
Risk-free interest rate		1.89%	—	1.89% – 2.17%		1.48% – 1.67%
Dividend yield		0%	—		0%		0%