Stock Based Compensation (Tables)

6 Months Ended

Jun. 30, 2016

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

The following table summarizes stock option activity under our 2013 Plan and related information during the six months ended June 30, 2016:

	Shares
	Subject to			Weighted-
	Outstanding			Average Exercise
	Options			Price Per Share
Balance at December 31, 2015		4,731,483		$	24.19
Options granted		1,465,086		$	29.82
Options exercised		(16,330	)	$	14.23
Options canceled		(210,869	)	$	28.59
Balance at June 30, 2016		5,969,370		$	25.44

Summary of PSO Activity

The following table summarizes PSO activity under our 2013 Plan and related information during the six months ended June 30, 2016:

	Shares
	Subject to		Weighted-
	Outstanding		Average Exercise
	Options		Price Per Share
Balance at December 31, 2015		—	$	—
Options granted		271,122	$	23.76
Options exercised		—	$	—
Options canceled		—	$	—
Balance at June 30, 2016		271,122	$	23.76

Fair Values of Employee Stock Options

The estimated grant date fair values of the employee stock options were calculated using the Black Scholes valuation model, based on the following assumptions:

	Three Months Ended June 30,			Six Months Ended June 30,
	2016	2015		2016	2015
Risk-free interest rate
Stock options	1.01% - 1.53%		1.85%	1.01% - 1.67%		1.70%
Performance stock options	1.34% - 1.50%	—		1.34% - 1.50%	—
Expected life
Stock options	5.0 years - 6.1 years	6.0 years		5.0 years - 7.0 years	6.0 years
Performance stock options	5.4 years - 6.4 years	—		5.4 years - 6.4 years	—
Expected volatility
Stock options	64% to 66%		64%	62% - 67%		65%
Performance stock options	65% to 66%	—		65% to 66%	—
Dividend yield
Stock options	—	—		—	—
Performance stock options	—	—		—	—

Summary of RSU Activity

The following table summarizes RSU activity, under our 2013 Plan and related information:

	Shares
	Subject to			Weighted-
	Outstanding			Average grant date
	RSUs			fair value per share
Balance at December 31, 2015		167,750		$	30.86
RSUs granted		495,806		$	28.01
RSUs released		(55,195	)	$	30.88
RSUs canceled		(22,372	)	$	30.62
Balance at June 30, 2016		585,989		$	28.46

Summary of PSU Activity

The following table summarizes PSU activity, under our 2013 Plan and related information:

	Shares
	Subject to			Weighted-
	Outstanding			Average grant date
	PSU's			fair value per share
Balance at December 31, 2015		205,261		$	29.33
PSUs granted		102,906			33.49
PSUs released		(13,170	)		50.00
PSUs canceled		(4,241	)		48.31
Balance at June 30, 2016		290,756			29.59

Classification of Stock-Based Compensation Expense

The table below sets forth the functional classification of stock-based compensation expense, net of estimated forfeitures, for the periods presented (in thousands):

	Three Months Ended June 30,				Six Months Ended June 30,
	2016		2015		2016		2015
Research and development	$	3,066	$	2,542	$	6,096	$	4,751
Selling, general and administrative		4,556		2,216		8,595		5,180
Total stock-based compensation	$	7,622	$	4,758	$	14,691	$	9,931