STOCK-BASED COMPENSATION (Tables)

6 Months Ended

Jun. 30, 2016


	Six Months Ended
	June 30,
	2016	2015
Option Plan Shares
Risk-free interest rates	1.48% - 1.69%	1.5% - 1.92%
Expected term (in years)	6.25 - 6.74	6.25
Expected volatility	58.9% - 59.4%	67.1% - 73.2%
Dividend yield	0%	0%
Weighted average fair value per share of options granted during the period	$3.17	$ 15.81
Market Measure-Based Shares
Risk-free interest rates	0.91%	(1)
Expected term (in years)	2.84	(1)
Expected volatility	68.3%	(1)
Dividend yield	0%	(1)
Weighted average fair value per share of stock purchase rights granted during the period	$2.32	(1)
ESPP Shares
Risk-free interest rates	0.41% - 0.8%	0.25% - 0.6%
Expected term (in years)	0.5 - 2	0.5 - 2
Expected volatility	70.1% - 92.7%	51.2% - 57.4%
Dividend yield	0%	0%
Weighted average fair value per share of stock purchase rights granted during the period	$ 3.08	$ 7.48

(1)

The Company did not issue market measure-based shares during the respective period.

Summary of stock option activity under the Stock Plans


				Weighted
		Weighted		Average
		Average		Remaining	Aggregate
		Exercise		Contractual	Intrinsic
Options	Shares	Price		Term (Years)	Value(1)
(Aggregate intrinsic value in thousands)
Outstanding, December 31, 2015	4,936,594	$	4.80	4.5
Granted	883,889		5.48
Exercised	(601,902)		0.92
Forfeited	(37,142)		11.85
Outstanding, June 30, 2016	5,181,439	$	5.32	5.1	$	39,971
Exercisable, June 30, 2016	3,911,528	$	3.85	3.7	$	34,049
Vested and expected to vest, June 30, 2016	5,105,018	$	5.26	5.0	$	39,580

(1)

The aggregate intrinsic value of options outstanding, exercisable and vested and expected to vest is calculated as the difference between the exercise price of the underlying options and the market price of the Company’s common stock for options that had exercise prices that were lower than the $12.25 market price of the Company’s common stock at June 30, 2016. The total intrinsic value of options exercised during the six months ended June 30, 2016 and 2015 was $4.6 million and $1.8 million, respectively.

Summary of restricted stock and restricted stock unit activity under the Stock Plans


		Weighted
	Restricted	Average Grant
	Shares	Date Fair Value
Outstanding, January 1, 2016	3,444,694	$	14.19
Granted	3,352,402		4.47
Released	(483,012)		16.06
Forfeited	(336,868)		11.59
Outstanding, June 30, 2016	5,977,216	$	8.49