Stockholders' Equity (Tables)

12 Months Ended

Dec. 31, 2016

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,
	2016		2015
Unvested restricted stock		1,297,054		969,758
Common stock options outstanding		1,267,329		1,684,783
Shares available for issuance under the 2013 Stock Plan		2,398,031		1,694,077
Shares available for issuance under the 2013 Employee Stock Purchase Plan		788,503		788,503
		5,750,917		5,137,121

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, 2015⁽¹⁾		959,864
Granted		997,956
Vested		(589,409	)
Cancelled		(71,357	)
Unvested at December 31, 2016		1,297,054

⁽¹⁾

Excludes 9,894 shares of unvested restricted stock remaining from the early exercise of stock options.

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, 2015		1,684,783		$	17.31		7.7	$	13,965
Granted		31,216			19.37
Exercised		(167,853	)		3.88
Cancelled		(280,817	)		30.50
Outstanding as of December 31, 2016		1,267,329		$	16.22		6.6	$	8,355
Exercisable as of December 31, 2016		955,971		$	13.88		6.4	$	7,500
Vested and expected to vest at December 31, 2016⁽¹⁾		1,243,380		$	16.02		6.6	$	8,330

⁽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 adjusted for estimated forfeitures.

⁽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, 2016, 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,
	2016		2015		2014
Cost of revenue	$	1,880	$	980	$	466
Selling and marketing		3,944		3,474		1,130
General and administrative		9,289		4,272		2,635
Research and development		4,411		2,450		1,758
Total	$	19,524	$	11,176	$	5,989

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

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			2014
Expected volatility		59.2	%		63.1	%		64.2	%
Risk-free interest rate		1.90	%		1.52	%		1.99	%
Expected option term (in years)		6.25			6.25			6.25
Expected dividend yield		0.0	%		0.0	%		0.0	%