Stock-based Compensation (Tables)

12 Months Ended

Dec. 31, 2018

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

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

Stock-based compensation expense related to the fair value measurement of awards granted to employees by financial line and by type of award is presented in the following table.



	Years Ended December 31,
	2018		2017		2016
	(In thousands)
Stock-based compensation expense by financial line:
Cost of revenue	$	87	$	158	$	113
General and administrative	3,266		2,218		$	2,057
Sales and marketing	694		821		$	524
Research and development	1,193		890		$	569
Total stock-based compensation expense	$	5,240	$	4,087	$	3,263

Stock-based compensation expense by type of award:
Options	$	3,873	$	3,331	$	3,005
RSUs	1,367		756		$	258
Total stock-based compensation expense	$	5,240	$	4,087	$	3,263

Schedule of Forfeiture Rates

The estimated forfeiture rates used in determining the expense in the table above are presented in the following table.



	For years ended December 31,
	2018	2017	2016
4-year options	14.866%	16.275%	13.513%
1-year options	—%	—%	—%

Schedule of Unamortized Compensation Cost and Weighted Average Service Period

The following table presents the unamortized compensation cost and weighted average service period of all unvested outstanding awards as of December 31, 2018.



	Unamortized Compensation Costs		Weighted Average Service Period
	(In thousands)		(In years)
Stock options	$	5,065	2.5
RSUs	2,128		2.2

Schedule of Grant Date Fair Value of Equity Instruments Vested

The total grant date fair value of stock options and RSUs vested during the period are presented in the following table.



	Years Ended December 31,
	2018		2017		2016
	(In thousands)
Stock options	$	3,607	$	3,375	2,977
RSUs	841		783		—
Total grant date fair value of stock options and RSUs vested during the period	$	4,448	$	4,158	2,977

Share-based Compensation, Stock Options, Activity

The following table summarizes the stock option activity under the 2016 Plan and 2008 Plan.



	Shares		Weighted Average Exercise Price		Weighted Average Remaining Contractual Life (in Years)	Aggregate Intrinsic Value ⁽¹⁾
	(In thousands, except for weighted average exercise price and weighted average remaining contractual life)
Balance, December 31, 2015	7,198		3.97
Granted	904		8.63
Exercised	(1,936	)	3.41			14,665
Forfeited	(283	)	5.30
Balance, December 31, 2016	5,883		4.81
Granted	677		9.57
Exercised	(1,226	)	4.49			6,798
Forfeited	(242	)	6.60
Balance, December 31, 2017	5,092		$	5.43	6.6	$	17,735
Granted	1,232		$	7.96
Exercised	(1,160	)	$	3.73
Forfeited	(183	)	$	3.98
Balance, December 31, 2018	4,982		$	6.36	6.56	$	6,572
Vested and exercisable as of December 31, 2018	3,193		$	5.44	5.39	$	6,124
Vested and exercisable as of December 31, 2018 and expected to vest thereafter	4,759		$	6.27	6.44	$	6,560

⁽¹⁾

The aggregate intrinsic value is calculated as the difference between the exercise price of the underlying options and the fair value of the Company’s common stock at the time of exercise. The aggregate intrinsic value at December 31, 2018 is calculated as the difference between the exercise price of the underlying options and the fair value of the Company’s common stock as of the end of the period.

Schedule of Share-based Compensation, Restricted Stock and Restricted Stock Units Activity

The following table summarizes the RSU activity under the 2016 Plan.



	Shares		Weighted Average Grant-Date Fair Value
	(In thousands, except for weighted average grant-date fair value)
Balance, December 31, 2015	—		—
Awarded	214		8.65
Balance, December 31, 2016	214		8.65
Awarded	162		10.14
Vested	(91	)	8.65
Forfeited	(11	)	8.52
Balance, December 31, 2017	274		9.54
Awarded	280		9.54
Vested	(90	)	9.33
Balance, December 31, 2018	463		8.49

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

The estimated grant date fair values of stock options granted to employees were calculated using the Black-Scholes option pricing model based on the assumptions in the following table.



	For years ended December 31,
	2018	2017	2016
Weighted average expected life (years)	4.19	4.50	4.38
Weighted average expected volatility	67.41%	80.22%	80.35%
Risk-free interest rate	2.48% – 3.01%	1.64% – 1.99%	1.03% – 1.32%
Weighted average dividend yield	—%	—%	—%

Schedule of Share Based Compensation, Awards Granted

On January 31, 2019 and February 1, 2019, the Company granted options and RSUs to certain officers. and on February 12, 2019, the Company granted options and RSUs to other employees. The options and RSUs granted are presented in the following table.



January 31, 2019 Grants	Shares	Exercise Price		Vesting Term⁽¹⁾	Expiration from Date of Grant
Options	228,571	$	7.60	4 years	10 years
RSUs	136,510	7.60		4 years	**
Total	365,081



February 2, 2019 Grants	Shares	Exercise Price		Vesting Term⁽¹⁾	Expiration from Date of Grant
Options	95,622	$	7.87	4 years	10 years
RSUs	19,059	$	7.87	4 years	**
Total	114,681



February 12, 2019 Grants	Shares	Exercise Price		Vesting Term⁽¹⁾	Expiration from Date of Grant
Options	67,888	$	7.70	4 years	10 years
RSUs	228,228	$	7.70	4 years	**
Total	296,116

** Not applicable.

⁽¹⁾ Any unvested options and RSUs are forfeited upon the employee’s termination.