Stockholders' Equity (Tables)

12 Months Ended

Dec. 31, 2017

Schedule of Number of Shares of Common Stock Reserved for Future Issuance

The Company has reserved for future issuance the following number of shares of common stock:

	December 31,
	2017		2016
Unvested restricted stock		1,164,040		1,297,054
Common stock options outstanding		666,717		1,267,329
Shares available for issuance under the 2013 Stock Plan		3,273,334		2,398,031
Shares available for issuance under the 2013 Employee Stock Purchase Plan		788,503		788,503
Total		5,892,594		5,750,917

Summary of Roll Forward of Restricted Stock Activity Pursuant to the 2010 and 2013 Stock Plan

The following table shows a roll forward of restricted stock activity pursuant to the 2010 Stock Plan and the 2013 Stock Plan:

	Number of Shares
Unvested at December 31, 2016		1,297,054
Granted		813,045
Vested		(720,074	)
Forfeited		(225,985	)
Unvested at December 31, 2017		1,164,040

Summary of Stock Option Activity Under the 2010 Stock Plan and the 2013 Stock Plan

A summary of stock option activity under the 2010 Stock Plan and the 2013 Stock Plan is as follows (in thousands, except share and per share amounts):

	Number of Shares			Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Term (In Years)		Aggregate Intrinsic Value⁽²⁾
Outstanding as of December 31, 2016		1,267,329		$	16.22		6.6	$	8,355
Granted		—			—
Exercised		(549,280	)		11.45
Forfeited		(51,332	)		24.39
Outstanding as of December 31, 2017		666,717		$	19.53		5.6	$	32,450
Exercisable as of December 31, 2017		595,665		$	18.37		5.5	$	29,684
Vested and expected to vest at December 31, 2017⁽¹⁾		666,717		$	19.53		5.6	$	32,450

⁽¹⁾	This represents the number of vested options plus the number of unvested options expected to vest at the respective dates, based on unvested options.

⁽²⁾	The aggregate intrinsic value was calculated based on the positive difference between the estimated fair value of the Company’s common stock on December 31, 2017, or the date of exercise, as appropriate, and the exercise price of the underlying options.

Recorded Stock-Based Compensation Expense in the Consolidated Statements of Operations and Comprehensive Loss

The Company recorded stock-based compensation expense in the consolidated statements of operations and comprehensive loss as follows (in thousands):

	Year Ended December 31,
	2017		2016		2015
Cost of revenue	$	2,214	$	1,880	$	980
Selling and marketing		4,162		3,944		3,474
General and administrative		10,887		9,289		4,272
Research and development		4,939		4,411		2,450
Total	$	22,202	$	19,524	$	11,176

Weighted-Average Assumptions Used to Estimate Fair Value of Stock Options Using Black-Scholes Option Pricing Model

There were no stock options granted during the year ended December 31, 2017. The weighted-average assumptions used to estimate the fair value of stock options using the Black-Scholes option pricing model were as follows:

	Year Ended December 31,
		2016			2015
Expected volatility			59.2	%		63.1	%
Risk-free interest rate			1.90	%		1.52	%
Expected option term (in years)			6.25			6.25
Expected dividend yield			0.0	%		0.0	%