Share-based compensation - Summary of Weighted Average Assumptions of RPSU Plan Units Under Equity Method (Detail) - Restricted share unit plan [member] - $ / shares	9 Months Ended
Sep. 30, 2020	Sep. 30, 2019
Disclosure of terms and conditions of share-based payment arrangement [line items]
Average fair value of units granted (per unit)	$ 0.55	$ 2.77
Expected life of units (years)	3 Years	3 Years
Expected forfeiture rate	0.60%	1.00%

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

No definition available.

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