Stock-based compensation - Changes in Performance Stock Units (Details) - PSUs	12 Months Ended
	Dec. 31, 2021 $ / shares shares
Restricted Stock Units Outstanding
Balance at beginning of period (in shares) | shares	53,147
Granted (in shares) | shares	65,304
Vested (in shares) | shares	0
Forfeited or expired (in shares) | shares	(2,701)
Balance at end of period (in shares) | shares	115,750
Weighted Average Grant Date Fair Value
Balance at beginning of period (in dollars per share) | $ / shares	$ 36.21
Granted (in dollars per share) | $ / shares	43.20
Vested (in dollars per share) | $ / shares	0
Forfeited (in dollars per share) | $ / shares	37.11
Balance at end of period (in dollars per share) | $ / shares	$ 40.13