Stock-based compensation - Assumptions (Details) - USD ($) $ / shares in Units, $ in Thousands																																															3 Months Ended		9 Months Ended
	Sep. 26, 2022	Sep. 23, 2022	Sep. 21, 2022	Sep. 06, 2022	Aug. 31, 2022	Aug. 29, 2022	Aug. 22, 2022	Aug. 19, 2022	Aug. 17, 2022	Aug. 08, 2022	Aug. 05, 2022	Aug. 01, 2022	Jul. 25, 2022	Jul. 06, 2022	Jul. 05, 2022	Jul. 01, 2022	Jun. 17, 2022	Jun. 13, 2022	Jun. 06, 2022	Jun. 01, 2022	May 31, 2022	May 16, 2022	May 11, 2022	May 09, 2022	May 02, 2022	Apr. 11, 2022	Apr. 07, 2022	Apr. 06, 2022	Apr. 01, 2022	Mar. 30, 2022	Feb. 25, 2022	Feb. 21, 2022	Feb. 14, 2022	Jan. 18, 2022	Jan. 16, 2022	Jan. 14, 2022	Jan. 04, 2022	Jan. 03, 2022	Oct. 01, 2021	Sep. 27, 2021	Aug. 23, 2021	Aug. 11, 2021	May 12, 2021	Mar. 08, 2021	Mar. 01, 2021	Feb. 26, 2021	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Share-based compensation
Volatility	113.00%	113.00%	113.00%	113.00%	113.00%	113.00%	113.00%	113.00%	112.00%	112.00%	112.00%	112.00%	112.00%	112.00%	112.00%	112.00%		112.00%	113.00%	113.00%	113.00%	113.00%	113.00%	113.00%	113.00%	114.00%	114.00%	114.00%	114.00%	114.00%	113.00%	113.00%	113.00%	114.00%	114.00%	114.00%	114.00%	114.00%	116.00%	116.00%	116.00%	116.00%	118.00%	117.00%	117.00%	117.00%
Risk-free interest rate	4.11%	3.91%	3.70%	3.42%	3.28%	3.24%	3.15%	3.09%	3.02%	2.88%	2.94%	2.65%	2.94%	2.98%	2.85%	2.90%		3.55%	3.05%	2.96%	2.84%	2.86%	2.92%	3.00%	3.03%	2.82%	2.72%	2.70%	2.53%	2.43%	1.91%	1.89%	1.94%	1.74%	1.73%	1.64%	1.47%	1.50%	1.10%	1.14%	0.92%	0.96%	1.11%	1.07%	0.92%	0.95%
Expected life	6 years 3 months	6 years 3 months	6 years 3 months	6 years 3 months	6 years 3 months	6 years 3 months	6 years 3 months	6 years 3 months	6 years 3 months	6 years 3 months	6 years 3 months	6 years 3 months	6 years 3 months	6 years 3 months	6 years 3 months	6 years 3 months		6 years 3 months	6 years 3 months	6 years 3 months	6 years 3 months	6 years 3 months	6 years 3 months	6 years 3 months	6 years 3 months	6 years 3 months	6 years 3 months	6 years 3 months	6 years 3 months	6 years 3 months	6 years 3 months	6 years 3 months	6 years 3 months	6 years 3 months	6 years 3 months	6 years 3 months	6 years 3 months	6 years 3 months	6 years 3 months	6 years 3 months	6 years 3 months			10 years	10 years	10 years
Dividend yield	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%		0.00%	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%
Common share price (in dollars per share)	$ 0.22	$ 0.21	$ 0.23	$ 0.21	$ 0.24	$ 0.26	$ 0.27	$ 0.27	$ 0.30	$ 0.38	$ 0.34	$ 0.28	$ 0.25	$ 0.25	$ 0.22	$ 0.21		$ 0.24	$ 0.26	$ 0.25	$ 0.23	$ 0.22	$ 0.20	$ 0.21	$ 0.25	$ 0.30	$ 0.31	$ 0.32	$ 0.33	$ 0.35	$ 0.35	$ 0.37	$ 0.29	$ 0.35	$ 0.35	$ 0.35	$ 0.35	$ 0.36	$ 0.57	$ 0.54	$ 0.50	$ 0.56	$ 0.78	$ 1.88	$ 2.06	$ 1.87
Strike price (in dollars per share)	$ 0.22	$ 0.21	$ 0.23	$ 0.21	$ 0.25	$ 0.27	$ 0.27	$ 0.27	$ 0.31	$ 0.39	$ 0.34	$ 0.28	$ 0.25	$ 0.26	$ 0.22	$ 0.21		$ 0.24	$ 0.26	$ 0.25	$ 0.24	$ 0.23	$ 0.20	$ 0.21	$ 0.25	$ 0.31	$ 0.31	$ 0.32	$ 0.34	$ 0.35	$ 0.35	$ 0.37	$ 0.30	$ 0.35	$ 0.35	$ 0.35	$ 0.35	$ 0.36	$ 0.58	$ 0.54	$ 0.50	$ 0.57	$ 0.78	$ 1.88	$ 2.06	$ 1.87
Forfeiture rate	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%		0.00%	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%
Stock-based compensation																																															$ 1,920	$ 1,438	$ 6,452	$ 4,503
Minimum
Share-based compensation
Expected life																																										6 years 2 months 4 days	6 years 2 months 15 days
Maximum
Share-based compensation
Expected life																																										6 years 3 months	6 years 2 months 19 days
Grantee One
Share-based compensation
Volatility																	112.00%
Risk-free interest rate																	3.02%
Expected life																	1 year 4 months 13 days
Dividend yield																	0.00%
Common share price (in dollars per share)																	$ 0.24
Strike price (in dollars per share)																	$ 0.24
Forfeiture rate																	0.00%
Grantee Two
Share-based compensation
Volatility																	112.00%
Risk-free interest rate																	3.02%
Expected life																	1 year 7 months 20 days
Dividend yield																	0.00%
Common share price (in dollars per share)																	$ 0.24
Strike price (in dollars per share)																	$ 0.24
Forfeiture rate																	0.00%
Grantee Three
Share-based compensation
Volatility																	112.00%
Risk-free interest rate																	3.35%
Expected life																	4 years 3 months 7 days
Dividend yield																	0.00%
Common share price (in dollars per share)																	$ 0.24
Strike price (in dollars per share)																	$ 0.24
Forfeiture rate																	0.00%