Share-based compensation - Summary of Status of Company's Stock Option Plan (Details) - $ / shares	9 Months Ended	12 Months Ended
Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Shares
Outstanding at beginning of period	5,329,515	7,042,377	7,042,377
-Cancelled	(107,447)		0
-Exercised	(1,373,905)		(1,967,562)
-Granted	463,754	254,700	254,700
Outstanding at end of period	4,311,917		5,329,515
Weighted Average Exercise Price
Outstanding at beginning of period	$ 1.06	$ 1.01	$ 1.01
-Cancelled	2.11		0
-Exercised	1.23		0.91
-Granted	1.71		1.11
Outstanding at end of period	$ 1.04		$ 1.06

No definition available.

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- Definition

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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- Definition

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

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- Definition

The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology.

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- Definition

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

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
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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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- Definition

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

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- Definition

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

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- Definition

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

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

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