Share-Based Payments (Tables)

12 Months Ended

Dec. 31, 2016

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Summary of share-based compensation expense (income)

The following table summarizes share-based compensation expense recorded in the years ended December 31, 2016, 2015 and 2014 (in thousands):

	2016		2015		2014
Outstanding employee and non-employee stock option grants	$	9,831	$	10,548	$	9,617
Outstanding restricted stock awards	8,064		504		3,549
Employee stock purchase plan	427		388		428
Total compensation cost	$	18,322	$	11,440	$	13,594

The table below presents share-based compensation expense for research and development as well as general and administration included in operating expenses in the years ended December 31, 2016, 2015 and 2014 (in thousands):

	2016		2015		2014
Research and development	$	7,558	$	5,145	$	6,204
General and administrative	10,764		6,295		7,390
Total compensation cost	$	18,322	$	11,440	$	13,594

Schedule of weighted average assumptions

The following table summarizes the weighted average assumptions the Company used in its fair value calculations at the date of grant:

	Weighted Average Assumptions
	Stock Options						Employee Stock Purchase Plan
	2016		2015		2014		2016		2015		2014
Expected volatility	58	%	59	%	66	%	57	%	59	%	63	%
Expected dividends	—		—		—		—		—		—
Expected life (years)	6.1		6.1		6.1		0.5		0.5		0.5
Risk-free interest rate	1.6	%	1.9	%	2.2	%	0.4	%	0.1	%	0.1	%

Schedule of stock option activity of company's stock plan

The following table presents stock option activity of the 2013 Plan and Prior Plans for the year ended December 31, 2016:

	Number of Stock Options (in thousands)		Weighted Average Exercise Price		Weighted Average Remaining Contractual Term (in years)	Aggregate Intrinsic Value (in thousands)
Outstanding at December 31, 2015	6,611		$	14.54
Granted	1,521		11.11
Exercised	(106	)	12.73
Forfeited	(362	)	13.51
Expired	(655	)	16.63
Outstanding at December 31, 2016	7,009		$	13.68	6.04	$	14,288
Exercisable at December 31, 2016	4,475		$	14.13	4.68	$	7,459
Vested or expected to vest at December 31, 2016	6,738		$	13.74	5.93	$	13,459

Schedule of nonvested shares of restricted stock

A summary of the status of nonvested shares of restricted stock as of December 31, 2016 and the changes during the year then ended are presented below (in thousands, except fair values):

	Number of Shares		Weighted Average Grant Date Fair Value
Nonvested at January 1, 2016	761		$	14.61
Granted	2,081		10.16
Vested	(519	)	14.55
Forfeited	(331	)	10.65
Nonvested at December 31, 2016	1,992		$	10.63

Summarized information about time-based or performance-based vesting schedules

Nonvested shares of restricted stock that have time-based or performance-based vesting schedules as of December 31, 2016 are summarized below (in thousands):

Vesting Schedule	Nonvested Shares
Time-based	575
Performance-based	1,417
Nonvested at December 31, 2016	1,992