Stockholders' Equity And Stock-Based Compensation (Narrative) (Details) - USD ($) $ / shares in Units, $ in Thousands				3 Months Ended		6 Months Ended
	Jun. 16, 2020	May 14, 2020	Jan. 01, 2019	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019	Nov. 30, 2017	Dec. 31, 2016	Dec. 31, 2014
Stockholders' Equity [Line Items]
Common stock, par value				$ 0.001		$ 0.001		$ 0.001
Common stock, shares issued				25,149,000		25,149,000		20,825,000
Rights issued in exchange for common stock, price per share		$ 0.15
Total stock-based compensation expense				$ 2,412	$ 2,699	$ 5,038	$ 5,060
Cash received from option exercises						$ 9	272
2017 Employee Stock Purchase Plan [Member]
Stockholders' Equity [Line Items]
Common stock, shares issued				43,224		43,224
Shares authorized				250,000		250,000
Increase in shares available for issuance threshold of common stock outstanding, number of shares						450,000
Increase in shares available for issuance threshold of common stock outstanding, percent outstanding						1.50%
Shares available for grant				396,971		396,971
2017 Inducement Equity Incentive Plan [Member]
Stockholders' Equity [Line Items]
Term period						10 years
Shares authorized									1,000,000
Shares available for grant				79,471		79,471
2017 Plan [Member]
Stockholders' Equity [Line Items]
Term period						10 years
Shares authorized				1,500,000		1,500,000
Additional common stock reserved for issuance			833,018
Increase in shares available for issuance threshold of common stock outstanding, number of shares						1,200,000
Increase in shares available for issuance threshold of common stock outstanding, percent outstanding						4.00%
Shares available for grant				359,658		359,658
Rights Offering [Member]
Stockholders' Equity [Line Items]
Common stock, par value				$ 0.001		$ 0.001
Value of warrants/rights	$ 29,500	$ 30,000		$ 29,500		$ 29,500
Common stock, shares issued	4,279,600			4,279,000		4,279,000
Right entitlement to holder		0.20506537
Warrants/rights outstanding	641,571			641,571		641,571
Exercise price of warrants/rights	$ 7.01	$ 7.01		$ 7.01		$ 7.01
Redemption per warrant	$ 0.01
Period the warrants are exercisable after issuance						30 days
Percentage requirement for warrant redemption	200.00%
Period of time required for redemption of warrants						10 days
Period of time warrant not able to be redeemed						6 months
First Vesting Portion [Member] | 2017 Inducement Equity Incentive Plan [Member]
Stockholders' Equity [Line Items]
Vesting percentage						25.00%
General and administrative [Member]
Stockholders' Equity [Line Items]
Total stock-based compensation expense				$ 1,515	1,660	$ 3,264	3,145
Research and development [Member]
Stockholders' Equity [Line Items]
Total stock-based compensation expense				$ 897	$ 1,039	$ 1,774	$ 1,915
Employee Stock Option [Member]
Stockholders' Equity [Line Items]
Options granted						1,823,810
Warrants exercised						750
Exercise price				$ 16.58		$ 16.58
Initial Public Offering [Member] | Rights Offering [Member]
Stockholders' Equity [Line Items]
Warrants/rights outstanding				121,609		121,609
Private Placement [Member]
Stockholders' Equity [Line Items]
Common stock, par value											$ 0.001
Chairman, Robert W. Duggan [Member] | Rights Offering [Member]
Stockholders' Equity [Line Items]
Ownership percentage				47.00%		47.00%		43.00%
Shares purchased						2,561,873
Common Stock
Stockholders' Equity [Line Items]
Warrants exercised					58,000	1,000	99,000
Common Stock | Rights Offering [Member]
Stockholders' Equity [Line Items]
Warrants/rights outstanding				641,571		641,571
MDB Capital Group, LLC [Member] | Initial Public Offering [Member]
Stockholders' Equity [Line Items]
Price per share										$ 5.00
Exercisable period of warrants or rights						5 years
Number of common shares called by issuance of warrants										574,985
MDB Capital Group, LLC [Member] | Private Placement [Member]
Stockholders' Equity [Line Items]
Price per share											$ 2.67
Warrants/rights outstanding				46,238		46,238
Exercisable period of warrants or rights						7 years
Number of common shares called by issuance of warrants											299,625