Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2019

Share-based Payment Arrangement [Abstract]

Schedule of Total Compensation Cost Recognized for all Stock-based Awards

The Company recognized stock-based compensation expense under the various Plans in the consolidated statements of operations and comprehensive loss as follows (in thousands):

	Year Ended December 31,
	2019		2018		2017
Research and development	$	9,943	$	12,669	$	14,227
Selling, general and administrative	13,052		11,900		14,021
	$	22,995	$	24,569	$	28,248

Schedule of Stock Option Valuation Assumptions

The fair value of each option issued to employees was estimated on the date of grant using the Black-Scholes option pricing model with the following weighted-average assumptions:

	Year Ended December 31,
	2019		2018		2017
Expected volatility	58.6	%	62.8	%	65.7	%
Expected term (in years)	6.0		6.0		6.0
Risk-free interest rate	2.39	%	2.70	%	2.13	%
Expected dividend yield	—	%	—	%	—	%

Summary of Stock Option Activity

The following table summarizes the stock option activity under the Company's stock option plans during the year ended December 31, 2019 (in thousands, except per share amounts and years):

	Number of Grants (in thousands)		Weighted- Average Exercise Price Per Share		Weighted- Average Contractual Life (in years)	Aggregate Intrinsic Value(1)
Outstanding at December 31, 2018	3,513		$	34.40
Granted	924		$	42.32
Exercised	(344	)	$	29.33
Canceled or forfeited	(273	)	$	41.64
Outstanding at December 31, 2019	3,820		$	36.26	6.81	$	64,146
Exercisable at December 31, 2019	2,400		$	33.76	5.80	$	46,258

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(1)

The aggregate intrinsic value is calculated as the difference between the exercise price of the underlying options and the estimated fair value of the common stock for the options that were in the money at December 31, 2019.

Schedule of Restricted Stock Unit Activity

The following table summarizes the restricted stock unit (RSU) activity under the 2013 Plan during the year ended December 31, 2019:

	Number of Stock Units (in thousands)		Weighted- Average Grant Date Fair Value Per Share
Unvested balance at December 31, 2018	372		$	36.53
Granted	216		$	41.43
Vested	(124	)	$	34.59
Forfeited	(67	)	$	40.25
Unvested balance at December 31, 2019	397		$	39.20

Performance Shares Units Nonvested Activity

The following table summarizes PSU activity under the 2013 Plan during the year ended December 31, 2019:

	Number of Stock Units (in thousands)		Weighted- Average Grant Date Fair Value Per Share
Unvested balance at December 31, 2018	236		$	31.42
Granted	—		$	—
Vested	(227	)	$	31.44
Forfeited	(9	)	$	31.09
Unvested balance at December 31, 2019	—		$	—