Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2018

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Schedule of Share-based Compensation, Stock Options, Activity

The following table summarizes stock option activity during the year ended December 31, 2018:

	Number of shares		Weighted average exercise price
Outstanding at December 31, 2017	2,490,465		$	9.59
Granted	—		$	—
Exercised	(5,042	)	$	4.33
Canceled	(45,509	)	$	11.35
Outstanding at December 31, 2018	2,439,914		$	9.57
Vested and expected to vest at December 31, 2018	2,439,607		$	9.57
Exercisable at December 31, 2018	2,416,389		$	9.54

Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions

The assumptions used in the valuation of stock options granted in the years ended December 31, 2018, 2017 and 2016, are summarized in the following table:

	Years Ended December 31,
	2018		2017		2016
Expected volatility	—	%	—	%	51	%
Expected life (years)	—		—		5.90
Risk free rate	—	%	—	%	1.35	%
Expected dividend yield	—	%	—	%	—	%

Schedule of Share-based Compensation, Restricted Stock, Award Activity

The Company’s restricted stock unit activity for the year ended December 31, 2018 was as follows:

	Restricted Stock Units
	Number of shares		Weighted Average Grant Date Fair Value
Unvested at December 31, 2017	2,073,440		$	9.14
Granted	1,827,626		$	4.55
Vested	(953,156	)	$	9.30
Canceled	(282,202	)	$	7.33
Unvested at December 31, 2018	2,665,708		$	6.12

Schedule of Share Based Compensation, Market Based Stock Units, Award Activity

The Company’s market-based stock unit activity for the year ended December 31, 2018 was as follows:

	Market-Based Stock Units
	Number of Shares		Weighted Average Grant Date Fair Value
Unvested at December 31, 2017	233,743		$	10.88
Units granted	320,000		$	7.19
Vested	(108,320	)	$	7.19
Canceled	(116,684	)	$	6.58
Unvested at December 31, 2018	328,739		$	10.03

Schedule of Share-based Compensation, Market Based Stock Units, Valuation Assumptions

The fair value of these market-based stock units was estimated on the date of grant using the Monte Carlo Simulation Valuation Model, which estimates the potential outcome of achieving the market condition based on simulated future stock prices, with the following assumptions:

	Years Ended December 31,
	2018			2017			2016
Expected volatility	65		%	54		%	49		%
Risk-free interest rate	2.40		%	1.50		%	0.90		%
Expected dividend	—		%	—		%	—		%
Weighted average fair value	$	7.19		$	13.82		$	4.94

Schedule of Share-based Compensation, Employee Stock Purchase Plan, Activity

A summary of ESPP activity for the years ended December 31, 2018, 2017, and 2016 is as follows (in thousands, except share and per share data):

	Years Ended December 31,
	2018		2017		2016
Shares issued	252,623		174,723		138,058
Weighted average fair value of shares issued	$	4.20	$	5.82	$	6.67
Employee purchases	$	1,061	$	1,016	$	921

Schedule of Share-based Payment Award, Employee Stock Purchase Plan, Valuation Assumptions

The assumptions used in the valuation for the years ended December 31, 2018, 2017 and 2016, are summarized in the following table:

	Years Ended December 31,
	2018		2017		2016
Expected volatility	73% - 54%		90% - 36%		69% - 52%
Expected life (years)	0.50		0.50		0.50
Risk free rate	2.6% - 2.1%		1.5% - 0.6%		0.6% - 0.4%
Expected dividend yield	—	%	—	%	—	%

Schedule of Employee Service Share-based Compensation, Allocation of Recognized Period Costs

Stock-based compensation was recognized in the consolidated statements of comprehensive loss as follows (in thousands):

	Years Ended December 31,
	2018		2017		2016
Cost of revenue	$	871	$	546	$	258
Sales and marketing	5,549		2,819		2,329
Research and development	2,470		3,039		2,482
General and administrative	2,807		5,766		4,167
Total stock-based compensation expense	$	11,697	$	12,170	$	9,236