Retirement plans - Schedule of Net Funded Status (Details) - USD ($) $ in Thousands	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair Value of Plan Assets	$ 337,902
Benefit Obligation	409,822
Funded Status	(71,920)
Retirement Plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair Value of Plan Assets	337,902	$ 386,108	$ 385,005
Benefit Obligation	409,822	462,466	$ 464,309
Funded Status	(71,920)	$ (76,358)
SERP
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair Value of Plan Assets	0
Benefit Obligation	44,162
Funded Status	(44,162)
All other
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair Value of Plan Assets	0
Benefit Obligation	279
Funded Status	(279)
TRP | Retirement Plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair Value of Plan Assets	337,902
Benefit Obligation	365,381
Funded Status	$ (27,479)