Stockholders' equity - Summary of SARs Activity (Details) - Stock Appreciation Rights - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2023	Mar. 31, 2022	Dec. 31, 2022
SARs Outstanding
Outstanding, beginning balance (in shares)	81,770
Granted (in shares)	0	0
Exercised (in shares)	0
Canceled (in shares)	(9,289)
Outstanding, ending balance (in shares)	72,481		81,770
Vested and expected to vest, SARs outstanding (in shares)	72,481
Exercisable, SARs outstanding (in shares)	71,706
Weighted Average Exercise Price
Outstanding, beginning balance (in USD per share)	$ 5.44
Granted (in USD per share)	0
Exercised (in USD per share)	0
Canceled (in USD per share)	6.58
Outstanding, ending balance (in USD per share)	5.29		$ 5.44
Vested and expected to vest, weighted average exercise price (in USD per shares)	5.29
Exercisable, weighted average exercise price (in USD per share)	$ 5.28
Outstanding, weighted average remaining contractual term	6 months 25 days		6 years 10 months 24 days
Outstanding, aggregate intrinsic value	$ 257		$ 418
Vested and expected to vest, weighted average remaining contractual term	6 months 25 days
Vested and expected to vest, aggregate intrinsic value	$ 257
Exercisable, weighted average remaining contractual term	6 months
Exercisable, aggregate intrinsic value	$ 254