Retirement plans - Schedule of Net Funded Status (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair Value of Plan Assets	$ 385,005
Benefit Obligation	464,309
Funded Status	(79,304)
Retirement Plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair Value of Plan Assets	385,005	$ 541,758	$ 552,996
Benefit Obligation	464,309	605,834	$ 646,662
Funded Status	(79,304)	$ (64,076)
SERP
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair Value of Plan Assets	0
Benefit Obligation	46,048
Funded Status	(46,048)
All other
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair Value of Plan Assets	0
Benefit Obligation	311
Funded Status	(311)
TRP | Retirement Plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair Value of Plan Assets	385,005
Benefit Obligation	417,950
Funded Status	$ (32,945)