Share-based compensation - Narrative (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Share-based compensation
Income tax benefit from compensation expense	$ 0	$ 500,000	$ 300,000	$ 1,600,000
Restricted stock units
Share-based compensation
Fair value of vested stock			1,400,000	3,700,000
Income tax benefit from compensation expense			300,000	800,000
Unrecognized share based compensation	2,200,000		$ 2,200,000
Weighted average period for recognition of unrecognized compensation cost (in years)			1 year 2 months 12 days
Long-term Incentive Plan
Share-based compensation
Payment award, low end of range			0.00%
Payment award, high end of range			200.00%
Measurement period for total return to shareholders (in years)			3 years
Award performance period (in years)			3 years
LTIP linked to TRS
Share-based compensation
Fair value of vested stock			$ 0	0
Unrecognized share based compensation	1,500,000		$ 1,500,000
Weighted average period for recognition of unrecognized compensation cost (in years)			1 year 7 months 6 days
LTIP awards linked to other performance conditions
Share-based compensation
Fair value of vested stock			$ 1,700,000	2,900,000
Income tax benefit from compensation expense			400,000	$ 600,000
Unrecognized share based compensation	$ 5,300,000		$ 5,300,000
Weighted average period for recognition of unrecognized compensation cost (in years)			1 year 9 months 18 days
Equity and Incentive Plan
Share-based compensation
Shares available for future issuance (in shares)	2,500,000		2,500,000
Number of share issuable upon vesting and achievement of performance goals (in shares)	900,000		900,000
Nonemployee Director Stock Plan
Share-based compensation
Shares available for future grant (in shares)	168,177		168,177