Share-based compensation - Schedule of Stock Options Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Share Options
Number of shares , Beginning Balance	60,000,000	144,000,000	114,000,000
Number of options granted			30,000,000
Number of options, Cancelled		(84,000,000)
Number of shares , Ending Balance	60,000,000	60,000,000	144,000,000	114,000,000
Number of shares , Vested	60,000,000
Number of shares , Exercisable	60,000,000
Share Based Compensation Arrangement By Share Based Payment Award Options Weighted Average Exercise Price [Abstract]
Weighted-Average per Share Exercise Price , Beginning Balance	$ 0.5	$ 0.69	$ 0.76
Weighted-Average per Share Exercise Price , Granted			0.4
Weighted-Average per Share Exercise Price , Cancelled		0.81
Weighted-Average per Share Exercise Price , Ending Balance	0.5	$ 0.5	$ 0.69	$ 0.76
Weighted-Average per Share Exercise Price, Vested	0.5
Weighted-Average per Share Exercise Price , Exercisable	$ 0.5
Share-Based Compensation Arrangement by Share-Based Payment Award Options Weighted Average Remaining Contractual Terms [Abstract]
Weighted Average Remaining Contractual Term	6 years 14 days	7 years 7 days	7 years 6 months 10 days	8 years 1 month 13 days
Weighted Average Remaining Contractual Term, Vested	6 years 14 days
Weighted Average Remaining Contractual Term, Exercisable	6 years 14 days
Share-Based Compensation Arrangements By Share-Based Payment Award Options Aggregate Intrinsic Value [Abstract]
Aggregate Intrinsic Value, Beginning balance	$ 0	$ 0
Aggregate Intrinsic Value, Ending balance	0	$ 0	$ 0
Aggregate Intrinsic Value, Vested	0
Aggregate Intrinsic Value, Exercisable	$ 0

Share Based Compensation Arrangement By Share Based Payment Award Options Weighted Average Exercise Price

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Share-Based Compensation Arrangement By Share-Based Payment Award Options Weighted Average Remaining Contractual Term

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Share-Based Compensation Arrangement By Share-Based Payment Award Options Aggregate Intrinsic Value

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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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- Definition

For presentations that combine terminations, 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 or that expired.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(iv)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

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Weighted average price of options that were either forfeited or expired.

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- Definition

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

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Amount by which the current fair value of the underlying stock exceeds the exercise price of options outstanding.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
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-Paragraph 2
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- Definition

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

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(i)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

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- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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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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Amount by which current fair value of underlying stock exceeds exercise price of fully vested and expected to vest options outstanding. Includes, but is not limited to, unvested options for which requisite service period has not been rendered but that are expected to vest based on achievement of performance condition, if forfeitures are recognized when they occur.

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
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-Subparagraph (e)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

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Number of fully vested and expected to vest options outstanding that can be converted into shares under option plan. Includes, but is not limited to, unvested options for which requisite service period has not been rendered but that are expected to vest based on achievement of performance condition, if forfeitures are recognized when they occur.

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Weighted-average exercise price, at which grantee can acquire shares reserved for issuance, for fully vested and expected to vest options outstanding. Includes, but is not limited to, unvested options for which requisite service period has not been rendered but that are expected to vest based on achievement of performance condition, if forfeitures are recognized when they occur.

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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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Amount of difference between fair value of the underlying shares reserved for issuance and exercise price of vested portions of options outstanding and currently exercisable.

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Weighted average remaining contractual term for vested portions of options outstanding and currently exercisable or convertible, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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

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

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