STOCKHOLDERS' EQUITY AND SHARE-BASED COMPENSATION EXPENSE (Tables)

12 Months Ended

Dec. 31, 2015

Stockholders Equity And Share Based Compensation Expense [Abstract]

Share-based compensation expense

The following table sets forth the share-based compensation expense included in the accompanying Consolidated Statements of Operations (in thousands):

	Year Ended December 31,
	2015		2014		2013
Costs of product sales	$	2,620	$	2,500	$	1,002
Research and development	1,951		2,266		1,331
Selling, general and administrative	10,414		7,645		5,394
Total share-based compensation expense	$	14,985	$	12,411	$	7,727

Fair value of options estimated at the date of grant with weighted-average assumptions

The fair value of options was estimated at the respective dates of grant using the BSM option pricing model with the following weighted‑average assumptions:

	Year Ended December 31,
	2015		2014		2013
Risk free interest rate	1.4	%	1.6	%	1.0	%
Expected dividend yield	—	%	—	%	—	%
Expected volatility	58	%	72	%	68	%
Expected option term (in years)	4.6		4.6		4.6

Stock options plan activity

Activity under the Company's stock plans for the year ended December 31, 2015 is as follows (in thousands, except per share amounts):

	Shares		Weighted-Average Exercise Price Per Share		Weighted-Average Remaining Contractual Terms	Aggregate Intrinsic Value
					(in years)	(in thousands)
Outstanding at December 31, 2014	4,195		$	6.23
Grants	504		11.00
Exercises	(1,138	)	7.24
Forfeitures or expirations	(156	)	9.36
Outstanding at December 31, 2015	3,405		$	6.46	3.61	$	13,662
Exercisable at December 31, 2015	2,091		$	5.65	2.58	$	9,995
Vested and expected to vest at December 31, 2015	3,178		$	6.31	3.47	$	13,184

Summary of outstanding and exercisable options

The following table summarizes information concerning currently outstanding and exercisable options at December 31, 2015:

Range of Exercise Prices				Options Outstanding				Options Exercisable
					Weighted-Average	Weighted-Average			Weighted-Average
					Remaining	Exercise Price			Exercise Price
Lower		Upper		Number	Contractual Life	Per Share		Number	Per Share
				(in thousands)	(in years)			(in thousands)
$	2.93	$	3.91	904	3.53	$	3.72	574	$	3.68
$	4.16	$	5.07	709	2.43	$	4.45	642	$	4.46
$	5.21	$	7.55	857	3.37	$	6.48	573	$	6.22
$	7.62	$	11.88	834	4.83	$	9.62	266	$	8.27
$	12.24	$	36.16	101	4.44	$	18.56	36	$	29.96
Total				3,405	3.61	$	6.46	2,091	$	5.65

Reserved shares

At December 31, 2015, the Company has shares reserved for future issuance as follows (in thousands):

Options outstanding	3,405
Options available for future grants	5,189
Convertible notes	17,857
Total at December 31, 2015	26,451

Summary of RSAs activity

The following tables summarize the Company's restricted stock activity for the year ended December 31, 2015 (in thousands, except per share amounts):

	Number of Shares		Weighted-Average Grant Date Fair Value per Share
Restricted stock units
Outstanding at December 31, 2014	2,395		$	6.30
Granted	1,396		10.04
Vested	(1,000	)	6.03
Forfeited	(265	)	7.39
Outstanding at December 31, 2015	2,526		$	8.36

Performance shares award outstanding activity

The following table summarizes the Company's PRSU activity for the year ended December 31, 2015 (in thousands, except per share amounts):

	Number of Shares		Weighted-Average Grant Date Fair Value per PRSU
Performance based restricted stock awards
Outstanding at December 31, 2014	723		$	6.83
Granted	399		12.07
Vested	(354	)	6.85
Forfeited	(65	)	6.38
Outstanding at December 31, 2015	703		$	9.84

Assumptions Used to Value Employees Stock Purchase Rights

During the years ended December 31, 2015 and 2014, the fair value of shares issued under the ESPP was estimated using the following assumptions:

	2015		2014
Risk free interest rate	0.23	%	0.07	%
Expected dividend yield	—	%	—	%
Expected volatility	58	%	72	%
Expected term (in years)	0.74		0.75