Stock incentive plans - Options outstanding under company's stock incentive plan (Details) - USD ($)	6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022
Options
Options outstanding, beginning of period	14	734
Granted	0	0
Forfeited	0	0
Exercised	0	(345)
Options outstanding, end of period	14	389
Options exercisable, end of period	14	389
Weighted Average Exercise Price
Options outstanding, beginning of period	$ 25.28	$ 25.63
Granted	0	0
Forfeited	0	0
Exercised	0	25.50
Options outstanding, end of period	25.28	25.74
Fair Value Per Share
Options outstanding, beginning of period	9.76	9.76
Granted	0	0
Forfeited	0	0
Exercised	0	0
Options outstanding, end of period	$ 9.76	$ 9.76
Intrinsic Value Options outstanding	$ 0	$ 0