STOCK-BASED COMPENSATION (Tables)

12 Months Ended

Dec. 31, 2017

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

Schedule of Employee Service Share-based Compensation, Allocation of Recognized Period Costs

The following table summarizes stock-based compensation expense incurred under the 2008 Plan and included in our consolidated statements of operations:

	Years Ended December 31,
(in thousands)	2017		2016		2015
Cost of sales	$	86	$	60	$	82
Research and development		677		112		109
Selling, general, and administrative		5,259		5,870		3,665
	$	6,022	$	6,042	$	3,856

Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions

For 2017, 2016, and 2015, the fair value of each option grant was estimated using the Black-Scholes option-pricing model, using the following assumptions:

	Years Ended December 31,
	2017	2016	2015
Expected option life (years)	5.33 - 7.00	5.50 - 6.25	5.50 - 6.25
Risk-free interest rate	1.93% - 2.33%	1.14% - 1.55%	1.31% - 1.82%
Expected stock price volatility	50.3% - 57.4%	49.4% - 51.7%	47.9% - 50.5%
Dividend yield	—	—	—

Schedule of Share-based Compansation, Stock Option And Restricted Stock, Activity

A summary of stock option activity under the 2008 Plan during the years ended December 31, 2017, 2016, and 2015 is presented below:

(in thousands, except per share and remaining term data)	Option Shares		Weighted Average Exercise Price		Weighted Average Grant-date Fair Value		Weighted Average Remaining Term (years)		Aggregate Intrinsic Value
Outstanding December 31, 2014		458	$	14.44				8.7	$	19,472
Granted		138		62.07	$	30.08
Exercised		(89)		9.24						3,937
Forfeited		(33)		11.81
Expired		-		-
Outstanding December 31, 2015		474	$	29.40				8.2	$	10,136
Granted		265		45.60	$	22.45
Exercised		(127)		11.79						5,837
Forfeited		(32)		47.84
Expired		(2)		139.32
Outstanding December 31, 2016		578	$	39.28				8.2	$	12,928
Granted		207		51.66	$	27.04
Exercised		(13)		15.92						542
Forfeited		(5)		53.29
Expired		-		-
Outstanding December 31, 2017		767	$	42.93				7.8	$	16,785
Exercisable at December 31, 2017		308	$	32.94				6.6	$	9,901

Nonvested Restricted Stock Shares Activity

A summary of RSA activity under the Plan during the years ended December 31, 2017, 2016, and 2015 is presented below:

(in thousands, except per share and remaining term data)	Shares		Weighted Average Grant Date  Fair Value		Weighted Average Remaining Term (years)
Unvested at December 31, 2014		63	$	19.34		2.6
Granted		28		67.26
Vested		(23)		15.82
Forfeited		(5)		19.41
Unvested at December 31, 2015		63	$	42.72		2.2
Granted		38		40.59
Vested		(30)		33.89
Forfeited		(8)		46.05
Unvested at December 31, 2016		63	$	45.72		2.2
Granted		50		49.51
Vested		(28)		44.49
Forfeited		-		-
Unvested at December 31, 2017		86	$	48.34		2.6