Share-Based Compensation - Outstanding and exercisable options (Details) - USD ($) $ / shares in Units, $ in Millions	6 Months Ended
Jun. 30, 2026	Jun. 30, 2025
Employee Stock Option
Outstanding and exercisable options, weighted average exercise price
Weighted average remaining contractual life (in years)	6 years 9 months 18 days	6 years 8 months 12 days
Weighted average remaining contractual life for vested options (in years)	5 years 6 months	5 years 9 months 18 days
Unrecognized compensation cost	$ 7.0	$ 5.5
Expected period for recognition	2 years 9 months 18 days	1 year 10 months 24 days
Plans 2011 and 2019 and 2021 Inducement
Outstanding and exercisable options, number of shares
Outstanding at end of year	13,920,076	11,282,070
Exercisable at end of year	8,741,233	8,146,545
Outstanding and exercisable options, weighted average exercise price
Outstanding at end of year	$ 3.48	$ 4.18
Exercisable at end of year	$ 4.4	$ 4.78
2011 Plan
Outstanding and exercisable options, number of shares
Outstanding at beginning of year	1,294,691	1,632,485
Exercised	(24,921)	(29,988)
Outstanding at end of year	1,269,770	1,602,497
Exercisable at end of year	1,269,770	1,602,497
Outstanding and exercisable options, weighted average exercise price
Outstanding at beginning of year	$ 2.23	$ 2.11
Exercised	1.12	1.12
Outstanding at end of year	2.25	2.12
Exercisable at end of year	$ 2.25	$ 2.12
2019 Plan
Outstanding and exercisable options, number of shares
Outstanding at beginning of year	8,591,306	7,604,606
Granted	2,807,000	1,511,400
Forfeited		(101,516)
Outstanding at end of year	11,398,306	9,014,490
Exercisable at end of year	6,978,257	6,162,757
Outstanding and exercisable options, weighted average exercise price
Outstanding at beginning of year	$ 4.21	$ 4.97
Granted	1.79	1.96
Forfeited		2.19
Outstanding at end of year	3.61	4.49
Exercisable at end of year	$ 4.69	$ 5.38
Inducement Plan
Outstanding and exercisable options, number of shares
Outstanding at beginning of year	710,000	496,000
Granted	542,000	244,000
Forfeited		(74,917)
Outstanding at end of year	1,252,000	665,083
Exercisable at end of year	493,206	381,291
Outstanding and exercisable options, weighted average exercise price
Outstanding at beginning of year	$ 4.76	$ 5.99
Granted	1.81	2.01
Forfeited		2.32
Outstanding at end of year	3.48	4.94
Exercisable at end of year	$ 5.9	$ 6.2

Amount of cost not yet recognized for nonvested award under share-based payment arrangement.

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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.

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The number of shares into which fully or partially vested stock options outstanding as of the balance sheet date can be currently converted under the option plan.

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The weighted-average price as of the balance sheet date at which grantees can acquire the shares reserved for issuance on vested portions of options outstanding and currently exercisable under the stock option plan.

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The number of shares under options that were cancelled during the reporting period as a result of occurrence of a terminating event specified in contractual agreements pertaining to the stock option plan.

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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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Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan.

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Weighted average price at which option holders acquired shares when converting their stock options into shares.

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Weighted average price at which grantees could have acquired the underlying shares with respect to stock options that were terminated.

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Weighted average per share amount at which grantees can acquire shares of common stock by exercise of options.

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Weighted-average contractual term remaining for option award outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

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Weighted-average contractual term remaining for fully vested and expected to vest exercisable or convertible options, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. Includes, but is not limited to, unvested option for which requisite service period has not been rendered but that is expected to vest based on achievement of performance condition, if forfeiture is recognized when it occurs.

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Number of share options (or share units) exercised during the current period.

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