Stockholders' Equity And Stock-Based Compensation (Tables)

9 Months Ended

Sep. 30, 2020

Stockholders' Equity [Line Items]

Summary Of Stock Option Activity

	Stock Options Outstanding
			Weighted
	Number		average
	of shares		exercise price
Balances — December 31, 2019	3,749,186	$	16.18
Options granted	1,933,560
Options exercised	(85,750)
Options canceled	(324,584)
Options expired	(65,086)
Balances — September 30, 2020	5,207,326	$	14.30
Exercisable — September 30, 2020	2,519,812	$	17.08

Summary Of Stock-Based Compensation Expense

	Three-Month Periods Ended				Nine-Month Periods Ended
	September 30,				September 30,
	2020		2019		2020		2019
General and administrative	$	1,465	$	1,735	$	4,729	$	4,881
Research and development		1,183		944		2,957		2,858
Total stock-based compensation expense	$	2,648	$	2,679	$	7,686	$	7,739

Employee Stock Option [Member]

Stockholders' Equity [Line Items]

Schedule Of Fair Value Of Employee Stock Options

	Three-Month Periods Ended September 30,		Nine-Month Periods Ended September 30,
	2020	2019	2020	2019
Expected term in years	5.8 - 6.1	5.8 - 6.1	5.3 - 6.1	0.4 - 6.1
Expected volatility	70%	70%	70%	70%
Risk-free interest rate	0.3 - 0.4%	1.4 - 1.7%	0.4 - 0.5%	1.4 - 2.6%
Dividend yield	—	—	—	—

2017 Employee Stock Purchase Plan [Member]

Stockholders' Equity [Line Items]

Schedule Of Fair Value Of Employee Stock Options

	Three-Month Periods Ended September 30,		Nine-Month Periods Ended September 30,
	2020	2019	2020	2019
Expected term in years	0.5 - 1.0	0.5 - 1.0	0.5 - 1.0	0.5 - 1.0
Expected volatility	70%	70%	70%	70%
Risk-free interest rate	0.1 - 0.1%	1.7 - 1.9%	0.1 - 1.0%	1.7 - 2.6%
Dividend yield	—	—	—