Stock Incentive Plans (Tables)

12 Months Ended

Dec. 31, 2016

Stock Incentive Plans

Summary of the Company's stock option activity

	Shares			Weighted- Average Exercise Price		Weighted Average Remaining Contractual Term (years)		Aggregate Intrinsic Value (in thousands)
Outstanding at December 31, 2015		1,723,554		$	6.66		7.92	$	4,267
Granted		1,068,845		$	4.49
Exercised		(230,019	)	$	2.00
Cancelled or forfeited		(292,211	)	$	6.60
Outstanding at December 31, 2016		2,270,169		$	6.11		8.14	$	613
Exercisable at December 31, 2016		851,769		$	5.79		6.64	$	607
Vested or expected to vest at December 31, 2016		2,177,976		$	6.12		8.09	$	613

Schedule of assumptions made based on the Black-Scholes option pricing model

	Year Ended December 31,
	2016			2015			2014
Weighted average expected volatility		72.0 - 73.9	%		73.6 - 86.8	%		75.2 - 83.4	%
Expected term (in years)		6.25			6.17 - 10.00			6.25 - 10.00
Risk free interest rate		1.24 - 2.00	%		0.92 - 2.45	%		1.71 - 3.01	%
Expected dividend yield		0	%		0	%		0	%