Stock Based Compensation (Tables)

9 Months Ended

Sep. 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 nine months ended September 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		1,586,286			29.37
Options exercised		(53,255	)		7.34
Options canceled		(376,365	)		29.66
Balance at September 30, 2016		5,888,149		$	25.39

Summary of PSO Activity

The following table summarizes PSO activity under our 2013 Plan and related information during the nine months ended September 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 September 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 September 30,			Nine Months Ended September 30,
	2016	2015		2016	2015
Risk-free interest rate
Stock options	1.03% - 1.33%		1.77%	1.01% - 1.60%		1.65%
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 - 6.1 years	6.0 years
Performance stock options	5.4 years - 6.4 years	—		5.4 years - 6.4 years	—
Expected volatility
Stock options	63% to 65%		65%	62% - 66%		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		(49,284	)		30.07
Balance at September 30, 2016		559,077		$	28.40

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
	PSUs			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		(8,945	)		49.34
Balance at September 30, 2016		286,052		$	29.25

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 September 30,				Nine Months Ended September 30,
	2016		2015		2016		2015
Research and development	$	3,465	$	3,252	$	9,561	$	8,004
Selling, general and administrative		4,307		2,849		12,903		8,028
Total stock-based compensation	$	7,772	$	6,101	$	22,464	$	16,032