Share-based compensation - Summary of Status of Company's Stock Option Plan (Details) - $ / shares	3 Months Ended	12 Months Ended
Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Shares
Outstanding at beginning of period	5,329,515	7,042,377	7,042,377
-Exercised	(155,000)		(1,967,562)
-Granted	415,478	0	254,700
Outstanding at end of period	5,589,993		5,329,515
Weighted Average Exercise Price
Outstanding at beginning of period	$ 1.06	$ 1.01	$ 1.01
-Exercised	1.09		0.91
-Granted	1.60		1.11
Outstanding at end of period	$ 1.10		$ 1.06

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- Definition

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

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

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

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