Equity (Tables)

12 Months Ended

Dec. 31, 2014

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

Stock options activity

Activity with respect to the stock options is summarized as follows:

	Number of Shares		Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Term (in years)	Aggregate Intrinsic Value
Outstanding at January 1, 2014	15,375,960		$	2.46
Granted	3,132,969		$	7.20
Exercised	(1,653,690	)	$	1.49
Unvested options forfeited	(296,680	)	$	4.09
Vested options expired	(84,332	)	$	0.81
Outstanding at December 31, 2014	16,474,227		$	3.43	7.3	$	133,360,210
Vested at December 31, 2014	9,280,650		$	1.97	6.5	$	88,716,569
Vested or expected to vest at December 31, 2014 (a)	16,198,892		$	3.38	7.3	$	131,953,654

(a) Includes forfeiture adjusted unvested shares.

Summary of stock options outstanding and exercisable

Following is a summary of stock options outstanding and exercisable at December 31, 2014:

	Options Outstanding				Options Exercisable
Range of Exercise Prices	Number outstanding	Weighted- Average Remaining Contractual Term (in years)	Weighted- Average Exercise Price		Number Exercisable	Weighted- Average Exercise Price
$0.50 - $0.76	632,500	4.4	$	0.72	632,500	$	0.72
$0.87 - $1.35	5,861,595	6.6	1.20		4,989,245	1.19
$1.40 - $2.29	1,460,201	5.0	1.64		1,338,532	1.65
$2.33 - $3.75	1,737,339	7.7	2.77		1,079,147	2.78
$3.95 - $5.99	3,365,030	8.4	5.15		977,415	5.10
$6.02- $9.13	3,287,562	8.8	7.06		263,811	6.47
$9.22 - $10.99	130,000	9.9	10.42		—	—
	16,474,227	7.3	$	3.43	9,280,650	$	1.97

Unvested Stock Options Roll Forward

A summary of the status of the Company’s unvested stock options as of December 31, 2014 is presented below:

Unvested Stock Options	Number of Shares		Weighted- Average Grant Date Fair Value
Unvested at January 1, 2014	8,568,228		$	1.94
Granted	3,132,969		$	4.18
Cancelled	(296,680	)	$	4.09
Vested	(4,210,940	)	$	1.58
Unvested at December 31, 2014	7,193,577		$	3.08

Fair value of options valuation assumptions

The assumptions used in calculating the fair value of options using the Black-Scholes-Merton option-pricing model are set forth in the following table:

	Year ended December 31,
	2014	2013	2012
Expected volatility	58.14 - 64.5%	61.41 - 64.77%	45.7 - 64.3%
Expected life (in years)	6	6	6
Expected dividend yield	—	—	—
Risk-free interest rate	1.64 - 1.96%	0.85 - 1.88%	0.62 - 1.77%

Restricted Stock Awards Roll Forward

Following is summary information for restricted stock awards for the years ended 2014 and 2013. Shares vest over a one to three year period. As of December 31, 2014, there was approximately $6,637,000 of total unrecognized stock-based compensation related to time-based, non-vested restricted stock.  That expense is expected to be recognized on a straight-line basis over a weighted-average period of 2.2 years.

Additionally, during the twelve months ended December 31, 2014, 8,411 shares of common stock valued at approximately $70,000 were issued under the 2006 Plan to a consultant in return for services performed.

	Number of Shares		Weighted-Average Grant Date Fair Value
Unvested at January 1, 2014	576,550		$	5.53
Granted	862,739		$	7.88
Vested	(209,671	)	$	5.71
Forfeited	(720	)	$	7.24
Unvested at December 31, 2014	1,228,898		$	5.53

Allocation of Share-based Compensation

For the years ended December 31, 2014, 2013, and 2012 the Company recognized stock-based compensation as follows (in thousands):  

	Year Ended December 31,
	2014		2013		2012
Cost of sales	$	322	$	279	$	98
Research and development	660		417		289
Selling, general and administrative	10,471		5,314		2,152
	$	11,453	$	6,010	$	2,539

Summary of warrants outstanding

Common Stock warrants activity and resulting balances for the years ended December 31, 2014 and 2013 are as follows:

	Number of Warrants		Weighted- Average Exercise Price per Warrant
Warrants outstanding at January 1, 2014	1,284,816		$	0.90
Warrants exercised	(1,242,416	)	$	0.90
Warrants outstanding at December 31, 2014	42,400		$	1.09