Stockholders' Equity And Stock-Based Compensation (Narrative) (Details)						1 Months Ended				12 Months Ended
	Jun. 30, 2021 USD ($) $ / shares shares	Feb. 05, 2021 $ / shares shares	Feb. 04, 2021 USD ($) shares	Jan. 01, 2021 shares	Jan. 01, 2020 shares	Jul. 31, 2021 USD ($)	May 31, 2021 shares	Mar. 31, 2021 shares	Jun. 30, 2020 USD ($) $ / shares shares	Dec. 31, 2021 USD ($) $ / shares shares	Dec. 31, 2020 USD ($) $ / shares shares	Dec. 31, 2019 USD ($) $ / shares shares	Dec. 31, 2017 shares	Dec. 31, 2014 $ / shares shares	Nov. 30, 2017 shares
Stockholders' Equity [Line Items]
Preferred stock, shares authorized										50,000,000	50,000,000
Preferred stock, par value | $ / shares										$ 0.001	$ 0.001
Preferred stock, shares outstanding										0	0	0
Common stock, par value | $ / shares										$ 0.001	$ 0.001
Common stock, shares authorized										500,000,000	500,000,000
Proceeds from issuance of common stock | $										$ 56,697,000	$ 29,434,000
Exercise price of warrants/rights | $ / shares											$ 7.01
Common stock, shares issued										29,716,000	25,550,000
Reduction to APIC from shares withheld for tax | $												$ (613,000)
Total stock-based compensation expense | $										$ 14,601,000	$ 10,075,000	11,287,000
Unrecognized compensation cost | $										$ 15,800,000
Weighted average remaining contractual life										2 years 8 months 12 days
2017 Employee Stock Purchase Plan [Member]
Stockholders' Equity [Line Items]
Common stock, shares issued										91,378	82,971
Shares authorized											250,000
Additional common stock reserved for issuance										383,250
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										649,096
2017 Inducement Equity Incentive Plan [Member]
Stockholders' Equity [Line Items]
Term period										10 years	10 years
Shares authorized															1,000,000
2017 Plan [Member]
Stockholders' Equity [Line Items]
Term period											10 years
Shares authorized											1,500,000
Additional common stock reserved for issuance				1,022,002	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										443,196
Rights Offering [Member]
Stockholders' Equity [Line Items]
Common stock, par value | $ / shares									$ 0.001
Value of warrants/rights | $									$ 30,000,000.0
Warrants/rights outstanding									641,571	0
Exercise price of warrants/rights | $ / shares									$ 7.01
Net proceeds | $			$ 4,500,000						$ 29,400,000
Number of common shares called by issuance of warrants									4,279,600
Number of warrants to purchase shares of common stock									0.15
Period of time warrant not able to be redeemed										6 months
Period the warrants are exercisable after issuance										30 days
Percentage requirement for warrant redemption									200.00%
Redemption per warrant | $ / shares		$ 0.01							$ 0.01
Period of time required for redemption of warrants										10 days
Warrants exercised		5,139	636,432
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 | $										$ 6,512,000	$ 4,875,000	6,583,000
Research And Development [Member]
Stockholders' Equity [Line Items]
Total stock-based compensation expense | $										5,211,000	4,013,000	3,821,000
Stock Options [Member]
Stockholders' Equity [Line Items]
Total stock-based compensation expense | $										4,100,000
Stock Options [Member] | 2017 Plan [Member]
Stockholders' Equity [Line Items]
Total stock-based compensation expense | $										$ 1,400,000
Stock Options [Member] | 2015, 2017 And Inducement Plans [Member]
Stockholders' Equity [Line Items]
Warrants exercised										53,731
Restricted Stock Units [Member]
Stockholders' Equity [Line Items]
Total stock-based compensation expense | $											86,000
Unrecognized compensation cost | $										$ 0
Restricted Stock Units [Member] | Granted In 2017 [Member]
Stockholders' Equity [Line Items]
Units granted during period													160,974
Total stock-based compensation expense | $										0	0	0
Unrecognized compensation cost | $										$ 0
Units outstanding										0
Common Stock Warrants [Member]
Stockholders' Equity [Line Items]
Warrants exercised										585,069
Time-Based Options [Member]
Stockholders' Equity [Line Items]
Total stock-based compensation expense | $										$ 9,235,000	8,739,000	10,895,000
Time-Based Options [Member] | 2015, 2017 And Inducement Plans [Member]
Stockholders' Equity [Line Items]
Warrants exercised										53,731
Total intrinsic value of options exercised | $										$ 800,000	1,600,000	1,000,000.0
Fair value of options granted | $										$ 15,100,000	6,700,000	8,400,000
Time-Based Options [Member] | Tranche One Through Four [Member]
Stockholders' Equity [Line Items]
Vesting percentage										25.00%
Performance Shares [Member]
Stockholders' Equity [Line Items]
Total stock-based compensation expense | $										$ 4,840,000	133,000	100,000
Performance Shares [Member] | 2017 And Inducement Plans [Member]
Stockholders' Equity [Line Items]
Fair value of options granted | $										2,500,000	$ 5,500,000	400,000
Private Placement [Member]
Stockholders' Equity [Line Items]
Common stock, par value | $ / shares														$ 0.001
Chairman, Robert W. Duggan [Member] | Rights Offering [Member]
Stockholders' Equity [Line Items]
Number of warrants to purchase shares of common stock									2,561,873
Chairman, Robert W. Duggan [Member] | Private Placement [Member]
Stockholders' Equity [Line Items]
Common stock, par value | $ / shares	$ 0.001
Shares sold	3,048,780
Price per share | $ / shares	$ 16.40
Aggregate issuance costs | $	$ 41,000,000.0
Proceeds from issuance of common stock | $	8,400,000					$ 8,400,000
Net proceeds | $	$ 50,000,000.0
Common stock, shares issued	3,048,780
Certain Employees [Member] | Restricted Stock Units [Member] | Granted In 2017 [Member]
Stockholders' Equity [Line Items]
Shares available for grant											68,800
Total stock-based compensation expense | $										$ 100,000	$ 300,000	$ 400,000
Certain Employees [Member] | Restricted Stock Units [Member] | First Vesting Portion [Member] | Granted In 2017 [Member]
Stockholders' Equity [Line Items]
Vesting percentage											50.00%
Cliff vest date										Jun. 01, 2019
Certain Employees [Member] | Restricted Stock Units [Member] | Second Vesting Portion [Member]
Stockholders' Equity [Line Items]
Cliff vest date										Jun. 01, 2021
Certain Employees [Member] | Restricted Stock Units [Member] | Second Vesting Portion [Member] | Granted In 2017 [Member]
Stockholders' Equity [Line Items]
Vesting percentage											50.00%
Common Stock
Stockholders' Equity [Line Items]
Shares issued										288,000
Warrants exercised										54,000	175,000	99,000
Common Stock | 2017 Employee Stock Purchase Plan [Member]
Stockholders' Equity [Line Items]
Additional common stock reserved for issuance							1,000,000
Common Stock | 2017 Inducement Equity Incentive Plan [Member]
Stockholders' Equity [Line Items]
Shares authorized										1,044,513
Robert W. Duggan [Member] | Private Placement [Member]
Stockholders' Equity [Line Items]
Price per share | $ / shares	$ 16.40
MDB Capital Group, LLC [Member] | Initial Public Offering [Member]
Stockholders' Equity [Line Items]
Warrants/rights outstanding										0
Number of common shares called by issuance of warrants												574,985
Price per share | $ / shares												$ 5.00
Common stock received from rights/warrants exercised								68,958
Warrants exercised								85,385
Exercisable period of warrants or rights										5 years
MDB Capital Group, LLC [Member] | Private Placement [Member]
Stockholders' Equity [Line Items]
Number of common shares called by issuance of warrants														299,625
Price per share | $ / shares														$ 2.67
Common stock received from rights/warrants exercised								40,563
Warrants exercised								45,638
Exercisable period of warrants or rights														7 years
Stifel, Nicolaus & Company Inc. [Member] | At the Market Offering [Member]
Stockholders' Equity [Line Items]
Value of warrants/rights | $			$ 60,000,000.0
Warrants/rights outstanding										288,490
Exercise price of warrants/rights | $ / shares										$ 27.73
Net proceeds | $										$ 7,400,000