The number of exercisable share warrants that may be converted as of the balance sheet date.

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

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Exercise price per share or per unit of warrants or rights outstanding.

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Number of warrants or rights outstanding.

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No definition available.

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Aggregate number of common shares reserved for future issuance.

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Face amount or stated value per share of common stock.

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Amount of cost to be recognized for option under share-based payment arrangement.

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Amount of cash inflow from exercise of option under share-based payment arrangement.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Gross number of share options (or share units) granted during the period.

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Number of options outstanding, including both vested and non-vested options.

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Per share amount of par value or stated value of stock classified as temporary equity. Temporary equity is a security with redemption features that are outside the control of the issuer, is not classified as an asset or liability in conformity with GAAP, and is not mandatorily redeemable.

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Stock-Based Compensation and warrants - Stock incentive plan and other information (Details) - USD ($)		1 Months Ended	12 Months Ended
	Sep. 05, 2019	Mar. 20, 2007	Dec. 31, 2020	Dec. 31, 2019	Nov. 16, 2020	Nov. 15, 2020	Sep. 17, 2020	Oct. 31, 2018	Oct. 10, 2018	Sep. 24, 2018	Sep. 07, 2017	Aug. 25, 2016	May 15, 2015	Oct. 10, 2014	Oct. 22, 2013	Nov. 02, 2010
Share-based Compensation Arrangement by Share-based Payment Award
Employee Service Share-based Compensation, Nonvested Awards, Compensation Not yet Recognized, Stock Options			$ 686,000
Proceeds from Stock Options Exercised			$ 0	$ 0
Temporary Equity, Par or Stated Value Per Share			$ 0.001	$ 0.001					$ 1,000
Class of Warrant or Right, Outstanding									13,672,173
Exercise price per warrant					$ 0.69	$ 1.38		$ 1.38	$ 1.38
Common stock, par value (in dollars per share)			$ 0.001	$ 0.001	$ 0.001
General and Administrative Expenses and Research and Development Expense [Member] \| Employees [Member]
Share-based Compensation Arrangement by Share-based Payment Award
Allocated Share-based Compensation Expense			$ 213,000	$ 295,000
Employees And Directors [Member]
Share-based Compensation Arrangement by Share-based Payment Award
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross			1,540,000	1,725,000
Consultant [Member] \| General and Administrative Expenses and Research and Development Expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award
Allocated Share-based Compensation Expense			$ 137,000	$ 45,000
Employees \| General and Administrative Expenses and Research and Development Expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award
Allocated Share-based Compensation Expense			$ 400,000	$ 500,000
2007 Stock Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number		71,429	5,145
2007 Stock Plan [Member] \| Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross		7,143
2010 Stock Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number			1,540,000													85,714
2010 Stock Plan [Member] \| Board of Directors [Member]
Share-based Compensation Arrangement by Share-based Payment Award
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number			2,452,273
2010 Stock Plan [Member] \| Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross	4,000,000
Common Stock, Capital Shares Reserved for Future Issuance										1,000,000	500,000	400,000	228,572		171,429
2010 Stock Plan [Member] \| Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross	1,000,000
Common Stock, Capital Shares Reserved for Future Issuance										500,000	400,000	228,572	171,429		85,714
2020 Stock Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number							4,000,000
Series A Warrants [Member]
Share-based Compensation Arrangement by Share-based Payment Award
Share-based Compensation Arrangement by Share-based Payment Award, Warrants, Exercisable Number														200,852