Stock-Based Compensation (Tables)

3 Months Ended

Mar. 31, 2018

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Summary of Assumptions Used to Estimate the Fair Value of Stock Options

The fair value of each option was estimated using the Black-Scholes model on the date of grant for the periods presented using the following assumptions:

	Three Months Ended March 31,
	2018		2017
Expected life (in years)		6.02	6.08 - 6.25
Risk-free interest rate	2.66%		2.05% - 2.14%
Volatility	50%		50%
Dividend yield	—		—

Summary of Stock Option and Restricted Stock Units Award Activity

A summary of the Company’s stock option and RSU award activity under the 2013 Plan is as follows:

				RSUs Outstanding					Options Outstanding
	Shares Available for Grant			Number of Shares			Weighted Average Grant Date Fair Value		Number of Shares			Weighted Average Exercise Price		Weighted Average Remaining Contractual Term (Years)		Aggregate Intrinsic Value (in thousands)
Balance as of December 31, 2017		4,425,155			5,194,292		$	12.26		7,412,228		$	10.36		6.09	$	25,415
Increase in shares authorized		3,727,989		—			—		—			—		—		—
Options granted		(801,000	)	—			—			801,000		$	13.10	—		—
Options exercised	—			—			—			(229,658	)	$	7.29	—		$	1,318
Options canceled or expired		69,869		—			—			(69,869	)	$	11.54	—		—
RSUs granted		(2,018,982	)		2,018,982		$	13.06	—			—		—		—
RSUs vested	—				(1,342,056	)	$	13.49	—			—		—		—
RSUs canceled or expired		155,766			(155,766	)	$	11.33	—			—		—		—
RSUs withheld for taxes		524,090		—			—		—			—		—		—
Balance as of March 31, 2018		6,082,887			5,715,452		$	12.28		7,913,701		$	10.72		6.22	$	30,327
Vested and exercisable as of March 31, 2018										5,459,769		$	10.23		5.07	$	27,111

Summary of Assumptions Used to Estimate the Fair Value of Employee Stock Purchase Plan

The fair value of the option feature is estimated using the Black-Scholes model for the period presented based on the following assumptions:

	Three Months Ended March 31,
	2018		2017
Expected life (in years)		0.50		0.50
Risk-free interest rate	1.42%		0.62%
Volatility	40%		50%
Dividend yield	—		—

Schedule of Stock Based Compensation Expense

The following table sets forth the total stock-based compensation expense resulting from stock options, RSUs and ESPP included in the Company’s condensed consolidated statements of operations (in thousands):

	Three Months Ended March 31,
	2018		2017
Cost of revenues	$	540	$	451
Sales and marketing		1,600		1,332
Research and development		1,827		2,011
General and administrative		3,829		3,962
Total stock-based compensation expense	$	7,796	$	7,756