Summary of significant accounting policies - Net income (loss) per share - (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities	7,357,134	5,956,827	6,064,344
Numerator:
Net (loss) income	$ (46,408)	$ (71,197)	$ 36,741
Denominator for basic net income (loss) per share:
Weighted average shares outstanding-basic	38,356,810	37,668,947	37,132,447
Denominator for diluted net income (loss) per share:
Weighted average shares outstanding-basic	38,356,810	37,668,947	37,132,447
Common stock options and restricted stock units			216,068
Weighted average shares outstanding-diluted	38,356,810	37,668,947	37,348,514
Financial instruments with off-balance sheet risk	$ 0
Unvested restricted common stock awards
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities	45,000	137,255	156,863
Unvested restricted common stock units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities	1,112,563	806,379	527,625
Stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities	6,199,571	5,013,193	5,379,856