Earnings (loss) per common share - Summary of computation of basic and diluted earnings (loss) per common share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2022	Sep. 30, 2021
Numerator:
Net income (loss)	$ (28,965)	$ 112,281	$ (49,021)	$ (47,420)	$ (42,652)	$ (39,383)	$ 34,295	$ (129,455)
Denominator:
Weighted average common shares for basic loss per common share	9,261			8,444			8,877	7,762
Effect of dilutive securities	0			0			328	0
Weighted average common shares for diluted loss per common share	9,261			8,444			9,205	7,762
(Loss) earnings per common share, basic	$ (3.13)			$ (5.62)			$ 3.86	$ (16.68)
(Loss) earnings per common share, diluted	$ (3.13)			$ (5.62)			$ 3.73	$ (16.68)