Stock-Based Compensation (Tables)

6 Months Ended

Jun. 30, 2016

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Schedule of Assumptions Used to Calculate Fair Value of Options Granted to Employees

The fair value of stock options granted to employees during the three and six months ended June 30, 2016 and 2015 was estimated at the date of grant using the following assumptions:

	Three Months Ended June 30,		Six Months Ended June 30,
	2016	2015	2016	2015
Risk-free interest rate	1.1 – 1.5%	1.5 – 1.8%	1.1 – 1.5%	1.5 – 1.8%
Expected dividend yield	0%	0%	0%	0%
Expected term	5.0 – 5.8 years	5.0 – 5.9 years	5.0 – 5.8 years	5.0 – 5.9 years
Expected volatility	67 – 69%	66 – 67%	67 – 69%	66 – 67%

Schedule of Recognized Stock-Based Compensation Expense

The Company recognized stock-based compensation expense during the three and six months ended June 30, 2016 and 2015 as follows:

	Three Months Ended June 30,					Six Months Ended June 30,
(in thousands)	2016			2015		2016			2015
Employee awards:
Research and development expense	$	1,804		$	2,369	$	3,672		$	4,335
Selling, general and administrative expense		2,773			2,576		4,438			3,954
Stock-based compensation expense for    employee awards		4,577			4,945		8,110			8,289
Stock-based compensation expense for    non-employee awards		—			22		1			48
Less: stock-based compensation expense   capitalized to inventory		(90	)		—		(220	)		—
Total stock-based compensation expense	$	4,487		$	4,967	$	7,891		$	8,337

Summary of Stock Option Activity

The following table summarizes stock option activity during the six months ended June 30, 2016:

						Weighted-Average Remaining		Aggregate
(in thousands, except per share amounts)	Shares			Weighted-Average Exercise Price		Contractual Term (in years)		Intrinsic Value
Outstanding at December 31, 2015		19,211		$	5.72		6.24	$	47,963
Granted		3,772		$	5.61
Exercised		(752	)	$	3.45
Forfeited		(584	)	$	7.05
Outstanding at June 30, 2016		21,647		$	5.75		6.38	$	16,475
Vested and expected to vest at June 30, 2016		21,260		$	5.73		6.32	$	16,470
Exercisable at June 30, 2016		15,797		$	5.31		5.37	$	16,224