Employee Equity-Based Compensation (Tables)

6 Months Ended

Jun. 30, 2019

Share-based Payment Arrangement [Abstract]

Stock Option Activity

The following table summarizes option activity under all plans during the six months ended June 30, 2019:

	Number of Shares		Weighted Average Exercise Price per Share
Options Outstanding January 1, 2019	8,090,636		$	12.22
Granted	1,594,929		12.36
Forfeited	(283,856	)	20.68
Exercised	(260,821	)	16.75
Expired	(38,878	)	23.16
Options Outstanding June 30, 2019	9,102,010		$	11.80

Inputs to Calculate Estimated Fair Value of Options Awarded

The table below summarizes the resulting weighted average inputs used to calculate the estimated fair value of options awarded during the periods shown below:

	Three Months Ended
	June 30,			June 30,
	2019			2018
Expected term (in years)	5.65			6.06
Volatility	58		%	64		%
Expected dividends	—			—
Risk free interest rates	2.38		%	2.82		%
Weighted average fair value	$	11.08		$	13.53

Stock Option Supplemental Information

The following table shows summary information for outstanding options and options that are exercisable (vested) as of June 30, 2019:

	Options Outstanding		Options Exercisable
Number of options	9,102,010		6,096,976
Weighted average remaining contractual term (in years)	5.83		4.47
Weighted average exercise price	$	11.80	$	8.94
Weighted average fair value	$	7.85	$	6.03
Aggregate intrinsic value (in thousands)	$	104,986	$	86,768

Restricted Stock Unit (RSU) Activity

The following table summarizes RSU and restricted stock award activity during the six months ended June 30, 2019:

	Number of Shares		Weighted Average Grant Date Fair Value per Share
Outstanding January 1, 2019	76,000		$	18.70
Granted	11,000		20.32
Forfeited	(55,000	)	20.24
Vested/released	(7,000	)	19.47
Outstanding June 30, 2019	25,000		15.81

Equity-Based Compensation Expenses

Equity-based compensation expense is summarized below (in thousands):

	Three Months Ended				Six Months Ended
	June 30,		June 30,		June 30,		June 30,
	2019		2018		2019		2018
Cost of sales	$	52	$	58	$	107	$	104
Research and development	802		838		2,329		2,450
Sales, general and administrative	2,027		2,513		3,842		6,457
	$	2,881	$	3,409	$	6,278	$	9,011