Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

Name:	us-gaap_AllocatedShareBasedCompensationExpense
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Weighted-average period over which cost not yet recognized is expected to be recognized for award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

Stock Based Compensation (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2022	Mar. 31, 2022	Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2022	Jun. 30, 2021
Share-based Compensation [Abstract]
Vesting period					4 years
Stock-based compensation expense					$ 1,590	$ 1,853
Payment of withholding taxes on shares issued upon conversion of RSUs					29	196
General and Administrative Expense [Member]
Share-based Compensation [Abstract]
Stock-based compensation expense	$ 487		$ 463		953	846
Research and Development Expense [Member]
Share-based Compensation [Abstract]
Stock-based compensation expense	$ 325		$ 511		$ 637	$ 1,007
Stock Options [Member]
Share-based Compensation [Abstract]
Term of award	10 years		10 years		10 years	10 years
Options granted (in shares)	801,004		779,500		801,004	779,500
Options granted, weighted average grant date fair value (in dollars per share)	$ 1.18		$ 3.45		$ 1.18	$ 3.45
Dividend yield					0.00%	0.00%
Volatility					86.00%	91.00%
Risk-free rate					3.00%	1.00%
Expected option term					6 years	6 years
Unrecognized stock-based compensation expense expected to be recognized related to unvested stock options	$ 5,242				$ 5,242
Weighted average amortization period					3 years 7 days
Common stock issued upon exercise of options (in shares)	0		0		0	0
Number of stock options returned to plan upon expiration (in shares)	255,000		255,000		390,000	390,000
Restricted Stock Units (RSUs) [Member]
Share-based Compensation [Abstract]
RSUs granted (in shares)	258,363	0	236,661	0
RSUs granted, weighted average fair values (in dollars per share)	$ 1.46		$ 4.61
Payment of withholding taxes on shares issued upon conversion of RSUs	$ 29		$ 196
Unrecognized stock-based compensation expense expected to be recognized related to unvested RSUs	$ 1,988				$ 1,988
Weighted average amortization period					2 years 11 months 4 days
Common stock issued upon vesting RSUs (in shares)	191,795	0	174,285	0
2013 Plan [Member]
Share-based Compensation [Abstract]
Shares available for grant (in shares)	1,435,929				1,435,929
2013 Plan [Member] \| Stock Options [Member]
Share-based Compensation [Abstract]
Vesting period					4 years
Term of award					10 years
2013 Plan [Member] \| Incentive Stock Options [Member] \| Minimum [Member]
Share-based Compensation [Abstract]
Exercise price of option granted as percentage of fair market value of shares at date of grant					100.00%
2013 Plan [Member] \| Incentive Stock Options [Member] \| Named Executive Officers [Member] \| Minimum [Member]
Share-based Compensation [Abstract]
Exercise price of option granted as percentage of fair market value of shares at date of grant					100.00%
2013 Plan [Member] \| Incentive Stock Options [Member] \| 10% Shareholder [Member] \| Minimum [Member]
Share-based Compensation [Abstract]
Exercise price of option granted as percentage of fair market value of shares at date of grant					110.00%
2013 Plan [Member] \| Nonqualified Stock Options [Member] \| Minimum [Member]
Share-based Compensation [Abstract]
Exercise price of option granted as percentage of fair market value of shares at date of grant					85.00%
2013 Plan [Member] \| Nonqualified Stock Options [Member] \| Named Executive Officers [Member] \| Minimum [Member]
Share-based Compensation [Abstract]
Exercise price of option granted as percentage of fair market value of shares at date of grant					100.00%
2013 Plan [Member] \| Restricted Stock Units (RSUs) [Member]
Share-based Compensation [Abstract]
Vesting period					4 years