Employee Stock Benefit Plans (Tables)

3 Months Ended

Mar. 31, 2018

Table Text Blocks

Share-based compensation expense reflected in the condensed consolidated statements of operations

The following table summarizes share-based compensation expense reflected in the condensed consolidated statements of operations for the three months ended March 31, 2018 and 2017 (in thousands):

	Three Months Ended
	March 31,
	2018		2017
Research and development		3,322		2,625
Selling, general and administrative		5,721		4,654
	$	9,043	$	7,279

Summary of stock option activity

		Weighted-
		Average
	Number of Shares	Fair Value
	(in thousands)
Outstanding at December 31, 2017	21,086	$	12.90
Granted	2,900		14.63
Exercised	(691)		8.97
Cancelled	(322)		15.02
Outstanding at March 31, 2018	22,973	$	13.21

Schedule of weighted-average assumptions used to estimate the fair value of the stock options using the Black-Scholes option-pricing model

	Three Months Ended
	March 31,
	2018		2017
Expected volatility	43.6	%	46.0	%
Expected term (in years)	6.0		6.0
Risk-free interest rate	2.7	%	2.0	%
Expected dividend yield	—	%	—	%

Summary of RSU activity

		Weighted-
		Average
	Number	Grant Date
	of Shares	Fair Value
Unvested as of December 31, 2017	2,277	$	15.08
Granted	1,536	$	14.61
Vested	(464)	$	15.19
Forfeited	(119)	$	14.83
Unvested as of March 31, 2018	3,230	$	14.85