STOCK-BASED COMPENSATION (Tables)

12 Months Ended

Dec. 31, 2018

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

Schedule of assumptions used to calculate the fair value of option grants

The Company used the following assumptions to calculate the fair value of option grants for the years ended December 31, 2018, 2017 and 2016.

	2018	2017	2016
Employee and Director Stock Options
Risk-free interest rate	2.17%	1.65 - 1.93%	0.90 - 1.78%
Expected option term (in years)	4.34	4.24 - 4.30	4.23 - 4.31
Expected stock price volatility	61.94%	51.67 - 59.59%	48.39 - 50.96%

Schedule of assumptions used to calculate the fair value of stock purchase rights granted under the ESPP

The Company used the following assumptions to calculate the fair value of stock purchase rights granted under the ESPP for the years ended December 31, 2018, 2017 and 2016:

	2018	2017	2016
Employee Stock Purchase Plan
Risk-free interest rate	2.05-2.50%	1.07 - 1.45%	0.49 - 0.60%
Expected option term (in years)	0.5	0.5	0.5
Expected stock price volatility	56.1-58.6%	52.2 - 82.0%	48.1 - 67.5%

Schedule of stock-based compensation expense recognized for stock options, stock awards, restricted stock units and the Company's employee stock purchase program (ESPP)

The following table presents stock‑based compensation expense recognized for stock options, restricted stock units and the ESPP in the Company’s Statements of Operations (in thousands):

	2018		2017		2016
Cost of sales	$	30	$	98	$	43
Research and development expense	446		710		496
Selling, general and administrative expense	9,963		12,157		16,633
Restructuring charges	2,146		51		—
Total	$	12,585	$	13,016	$	17,172

Summary of the options activity

The following table summarize the activity for the year ended December 31, 2018 under the 2014 Plan:

	Shares		Weighted Average Exercise Price
Options outstanding at December 31, 2017	3,455,769		$	14.24
Options granted	75,304		8.55
Options exercised	—		—
Options forfeited	(1,270,762	)	13.20
Options expired	(798,842	)	17.83
Options outstanding at December 31, 2018	1,461,469		$	12.90
Options vested and expected to vest at December 31, 2018	1,461,469		$	12.90
Options exercisable at December 31, 2018	808,141		$	14.30

	Weighted- Average Remaining Contractual Term (years)	Aggregate Intrinsic Value (in thousands)
Options outstanding at December 31, 2018	6.75	$	—
Options vested and expected to vest at December 31, 2018	6.75	$	—
Options exercisable at December 31, 2018	6.04	$	—

The following tables summarize the activity for the year ended December 31, 2018 under the 2004 Plan:

	Shares		Weighted- Average Exercise Price
Options outstanding at December 31, 2017	1,786,041		$	7.62
Options granted	—		—
Options exercised	(277,443	)	5.37
Options forfeited	(6,965	)	12.69
Options expired	(332,221	)	9.56
Options outstanding at December 31, 2018	1,169,412		$	7.57
Options vested and expected to vest at December 31, 2018	1,169,412		$	7.57
Options exercisable at December 31, 2018	1,169,412		$	7.57

	Weighted- Average Remaining Contractual Term (years)	Aggregate Intrinsic Value (in thousands)
Options outstanding at December 31, 2018	1.78	$	29
Options vested and expected to vest at December 31, 2018	1.78	$	29
Options exercisable at December 31, 2018	1.78	$	29

Schedule of restricted stock units and performance-based restricted stock units activity

The following table summarizes the PSU activity for the year ended December 31, 2018 under the 2014 Plan (in thousands, except per share data):

			Weighted		Weighted
			Average		Average
			Grant Date		Remaining
			Fair		Contractual	Aggregate
	Number of		Value		Term	Intrinsic Value
	Shares		Per Share		(in years)	(in 000s)
Non-vested performance-based restricted stock units at December 31, 2017	—		$	—
Granted	523,187		10.58
Vested	—		—
Forfeited	(148,363	)	11.68
Non-vested performance-based restricted stock units at December 31, 2018	374,824		$	10.14	2.09	1,353

	Number of Shares		Weighted Average Grant Date Fair  Value Per Share		Weighted Average Remaining Contractual Term (in years)
Non-vested restricted stock units at December 31, 2017	1,166,046		$	10.69
Granted	1,897,661		6.84
Vested	(539,898	)	9.77
Forfeited	(585,021	)	9.05
Non-vested restricted stock units at December 31, 2018	1,938,788		$	6.94	1.24