Share-based payments - Summary of Restricted Common Stock Unit Activity (Details) - Restricted stock unit	12 Months Ended
	Dec. 31, 2021 $ / shares shares
Units
Outstanding at January 1, 2020 (in shares) | shares	230,928
Granted (in shares) | shares	240,811
Vested/Converted (in shares) | shares	(121,896)
Forfeited (in shares) | shares	(11,143)
Outstanding at December 31, 2020 (in shares) | shares	338,700
Nonvested balance at end of period (in shares) | shares	299,889
Weighted-Average Grant-Date Fair Value per Share ($)
Outstanding at January 1, 2020 (in usd per share) | $ / shares	$ 41.25
Granted (in usd per share) | $ / shares	54.45
Vested/Converted (in usd per share) | $ / shares	42.68
Forfeited (in usd per share) | $ / shares	48.18
Outstanding at December 31, 2020 (in usd per share) | $ / shares	49.89
Nonvested balance at end of period (in usd per share) | $ / shares	$ 50.75