STOCK-BASED COMPENSATION (Tables)

12 Months Ended

Dec. 31, 2016

Stock-based compensation

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

	2016	2015	2014
Employee and Director Stock Options
Risk-free interest rate	0.90 - 1.78%	1.04 - 1.59%	1.26 - 1.51%
Dividend yield	None	None	None
Expected option term (in years)	4.23 - 4.31	4.30 - 4.31	4.33 - 4.41
Expected stock price volatility	48.39 - 50.96%	44.78 - 50.45%	42.6 - 49.0%

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

	2016	2015	2014
Employee Stock Purchase Plan
Risk-free interest rate	0.49 - 0.60%	0.07 - 0.41%	0.06 - 0.08%
Dividend yield	None	None	None
Expected option term (in years)	0.5	0.5	0.5
Expected stock price volatility	48.1 - 67.5%	42.7 - 58.2%	44.8 - 61.4%

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):

	2016		2015		2014
Cost of sales	$	43	$	21	$	14
Research and development expense		496		277		258
Selling, general and administrative expense		16,633		13,930		8,658
Total	$	17,172	$	14,228	$	8,930

The 2004 Plan

Stock-based compensation

Summary of the options activity under the plan

		Weighted-
		Average
		Exercise
	Shares	Price
Options outstanding at December 31, 2015	4,698,798	$	8.05
Options granted	—		—
Options exercised	(536,436)		7.58
Options forfeited	(88,681)		10.10
Options expired	(6,834)		7.23
Options outstanding at December 31, 2016	4,066,847	$	8.07
Options vested and expected to vest at December 31, 2016	4,046,646	$	8.04
Options exercisable at December 31, 2016	3,662,060	$	7.65

	Weighted-
	Average
	Remaining		Aggregate
	Contractual		Intrinsic Value
	Term (Years)		(in thousands)
Options outstanding at  December 31, 2016	5.38	$	40,476
Options vested and expected to vest at  December 31, 2016	5.37	$	40,366
Options exercisable at  December 31, 2016	5.21	$	37,977

Schedule of restricted stock units

		Weighted		Weighted
		Average		Average
		Grant Date		Remaining
	Number of	Fair Value		Contractual Term
	Shares	Per Share		(In years)
Non-vested restricted stock units at December 31, 2015	269,114	$	10.90
Granted	—		—
Vested	(165,524)		9.94
Forfeited	(16,292)		11.01
Non-vested restricted stock units at  December 31, 2016	87,298	$	12.69	0.92

The 2014 Plan

Stock-based compensation

Summary of the options activity under the plan

		Weighted
		Average
		Exercise
	Shares	Price
Options outstanding at December 31, 2015	2,522,225	$	17.59
Options granted	2,139,939		16.98
Options exercised	(175,427)		14.98
Options forfeited	(462,989)		16.06
Options expired	(21,280)		18.43
Options outstanding at December 31, 2016	4,002,468	$	17.56
Options vested and expected to vest at December 31, 2016	3,439,346	$	17.51
Options exercisable at December 31, 2016	1,306,524	$	17.27

	Weighted-
	Average
	Remaining	Aggregate
	Contractual	Intrinsic Value
	Term (Years)	(in thousands)
Options outstanding at December 31, 2016	8.33	$	5,414
Options vested and expected to vest at December 31, 2016	8.25	$	4,706
Options exercisable at December 31, 2016	7.63	$	1,914

Schedule of restricted stock units

		Weighted		Weighted
		Average		Average
		Grant Date		Remaining
	Number of	Fair Value		Contractual Term
	Shares	Per Share		(In years)
Non-vested restricted stock units at December 31, 2015	411,115	$	18.43
Granted	520,325	$	16.20
Vested	(281,110)		17.62
Forfeited	(80,839)		16.90
Non-vested restricted stock units at December 31, 2016	569,491	$	17.01	1.6