Stock Based Compensation (Tables)

3 Months Ended

Mar. 31, 2016

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Stock Options

The following table summarizes stock option activity under our 2013 Plan and related information:

	Shares
	Subject to			Weighted-
	Outstanding			Average Exercise
	Options			Price Per Share
Balance at December 31, 2015		4,731,483		$	24.19
Options granted		980,215		$	32.51
Options exercised		(10,984	)	$	15.52
Options canceled		(85,230	)	$	28.85
Balance at March 31, 2016		5,615,484		$	25.59

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

	For the Three Months Ended March 31,
	2016			2015
Risk-free interest rate		1.61	%		1.54	%
Expected life	6.0 years			6.0 years
Expected volatility		64	%		66	%
Dividend yield	—			—

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:

	For the Three Months Ended March 31,
	2016			2015
Risk-free interest rate		1.61	%		1.54	%
Expected life	6.0 years			6.0 years
Expected volatility		64	%		66	%
Dividend yield	—			—

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		215,655		$	33.49
RSUs released		(55,195	)	$	30.88
RSUs canceled		(9,982	)	$	31.67
Balance at March 31, 2016		318,228		$	32.62

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		(1,303	)		49.44
Balance at March 31, 2016		293,694			29.77

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):

	For the Three Months Ended March 31,
	2016		2015
Research and development	$	3,030	$	2,209
Selling, general and administrative		4,039		2,963
Total stock-based compensation	$	7,069	$	5,172