Stock Based Compensation (Tables)

6 Months Ended

Jun. 30, 2019

Share-based Payment Arrangement [Abstract]

Schedule of Share-based Compensation Related to Restricted Stock Awards and Stock Options

For the three and six months ended June 30, 2019 and 2018, the Company recorded stock-based compensation expense related to stock options and restricted stock awards as follows (in thousands):

	For the three months ended				For the six months ended
	June 30,				June 30,
	2019		2018		2019		2018
General and administrative expense	$	6,892	$	7,035	$	15,929	$	12,807
Research and development expense		1,481		1,309		2,565		2,982
Sales and marketing expense		245		–		413		-
Total stock-based compensation expense	$	8,618	$	8,344	$	18,907	$	15,789

Schedule of Share-based Compensation, Stock Options, Activity

A summary of the Company’s employee and non-employee stock option activity for the six months ended June 30, 2019 is presented below:

	Number of shares			Weighted-Average Exercise Price
Outstanding – December 31, 2018		6,499,885		$	14.02
Granted		767,201		$	14.36
Exercised (1)		(292,417	)	$	3.99
Forfeited		(370,208	)	$	7.81
Outstanding – June 30, 2019		6,604,461		$	14.30
Options exercisable – June 30, 2019		4,567,527		$	12.11
Weighted-average grant date fair value of options granted during the six months ended June 30, 2019				$	10.28

(1) The number of exercised options includes shares withheld on behalf of employees to satisfy minimum statutory tax withholding requirements.

Schedule of Share-based Compensation, Restricted Stock Activity

A summary of the Company’s employee and non-employee restricted-stock activity for the six months ended June 30, 2019 is presented below:

	Number of shares			Weighted-Average Grant-Date Fair Value
Unvested - December 31, 2018		651,110		$	23.65
Granted		75,000		$	10.97
Vested (1)		(187,663	)	$	28.83
Forfeited		(45,000	)	$	22.46
Unvested – June 30, 2019		493,447		$	22.66

(1) The number of vested restricted stock units includes shares that were withheld on behalf of employees to satisfy the minimum statutory tax withholding requirements.