Stock-Based Compensation (Tables)

3 Months Ended

Mar. 31, 2019

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

Schedule of Valuation Assumptions

The fair value of each option award is estimated on the date of grant using the Black-Scholes option-pricing formula that uses assumptions noted in the following table. Expected volatilities and risk-free interest rates are based upon the expected life of the grant.

	Three Months Ended March 31,
Assumptions	2019		2018
Expected dividends	—		—
Risk-free rate	2.47	%	2.32	%
Expected volatility	57.8%-60.2%		60.5%-60.9%
Expected term (in years)	3.2-3.3 years		3.2 - 3.3 years

Schedule of Stock Option Activity

A summary of option activity under the 1999 Director Stock Option Plan, 2009 Equity Incentive Plan, and the 2016 Equity Incentive Plan as of March 31, 2019 and changes during the period are presented below:

	Number of Options	Weighted Average Exercise Price
Outstanding as of January 1, 2019	4,352,391	$	4.61
Issued	1,866,855	1.60
Exercised	—	—
Forfeited	(113,627)	4.84
Expired	—	—
Outstanding as of March 31, 2019	6,105,619	$	3.68
Exercisable as of March 31, 2019	3,601,093	$	4.65

Schedule of Stock Options Outstanding and Exercisable

The following tables summarize information regarding options outstanding and exercisable at March 31, 2019:

Outstanding:

Range of Exercise Prices	Stock Options Outstanding	Weighted Average Exercise Price		Weighted Average Remaining Contractual Life
$0.79 - $1.50	1,652,250	$	1.08	3.47
$1.51 - $5.50	2,642,313	2.17		9.22
$5.51 - $10.67	1,811,056	8.25		6.73
Total	6,105,619	$	3.68	6.93

Exercisable: 

Range of Exercise Prices	Stock Options Exercisable	Weighted Average Exercise Price
$0.79 - $1.50	1,510,000	$	1.06
$1.51 - $5.50	452,961	3.17
$5.51 - $10.67	1,638,132	8.36
Total	3,601,093	$	4.65

Schedule of Nonvested Restricted Stock Units Activity

The following table summarizes the number of unvested RSUs and their weighted average exercise price for the three months ended March 31, 2019.

	Number of RSUs	Weighted Average Grant Date Fair Value
Non-vested balance at January 1, 2019	175,591	$	4.78
Changes during the period:
Shares granted	—	—
Shares vested	(71,206)	5.20
Shares forfeited	(3,612)	3.53
Non-vested balance at March 31, 2019	100,773	$	4.53