Share-Based Payments (Tables)

9 Months Ended

Sep. 30, 2016

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

Summary of Stock-Based Compensation Expense

Stock-based compensation expense by award type was as follows (in thousands):

	Three Months Ended September 30,				Nine Months Ended September 30,
	2016		2015		2016		2015
Stock options	$	1,932	$	475	$	2,825	$	1,708
Restricted stock	50		55		155		88
Restricted stock units	156		99		354		99
Employee stock purchase plan	6		—		17		—
	$	2,144	$	629	$	3,351	$	1,895

Summary of Stock Option Activity and Related Information

A summary of the stock option activity is presented below:

	Shares		Weighted-Average Exercise Price
Outstanding at December 31, 2015	1,803,574		$	6.28
Granted	1,747,495		1.69
Exercised	(341,526	)	0.49
Cancelled or forfeited	(494,787	)	3.30
Outstanding at September 30, 2016	2,714,756		$	4.60
Exercisable at September 30, 2016	1,606,002		$	5.18
Vested and expected to vest at September 30, 2016(1)	2,530,001		$	4.69

(1) Represents the number of vested options, plus the number of unvested options expected to vest.

Summary of Status and Changes of Unvested Restricted Stock

A summary of the unvested restricted stock is presented below:

	Restricted Stock		Weighted-Average Grant Date Fair Value
Unvested at December 31, 2015	41,657		$	11.05
Vested	(15,077	)	10.38
Unvested at September 30, 2016	26,580		$	11.43

Schedule of Share-based Compensation, Restricted Stock and Restricted Stock Units Activity

A summary of the restricted stock units is presented below:

	Restricted Stock Units		Weighted-Average Grant Date Fair Value
Unvested at December 31, 2015	150,932		$	2.85
Vested	(131,166	)	2.83
Cancelled	(13,100	)	2.76
Unvested at September 30, 2016	6,666		$	3.43