v3.26.1
Retirement Benefits
 6 Months Ended
Jun. 30, 2026
Retirement Benefits [Abstract]  
Retirement Benefits Retirement Benefits
The components of the net periodic pension benefit cost were as follows:
Three Months EndedSix Months Ended
June 30, 2026June 30, 2025June 30, 2026June 30, 2025
(Dollars in thousands)
Service cost$1,551 $1,968 $3,133 $3,912 
Interest cost7,614 8,177 15,295 16,296 
Expected return on plan assets(10,410)(10,256)(20,819)(20,513)
Amortization of prior service (credit) cost (15)5 (28)13 
Amortization of actuarial losses1,785 1,883 3,567 3,776 
Net periodic benefit cost $525 $1,777 $1,148 $3,484 
 
The components of the net periodic other postretirement benefit (credit) cost were as follows:
Three Months EndedSix Months Ended
June 30, 2026June 30, 2025June 30, 2026June 30, 2025
(Dollars in thousands)
Service cost$2 $6 $5 $10 
Interest cost91 151 183 302 
Amortization of prior service credit(17)(14)(33)(29)
Amortization of actuarial gains(157)(86)(314)(172)
Net periodic benefit (credit) cost $(81)$57 $(159)$111