v3.26.1
Pension and Postretirement Benefit Costs (Tables)
 6 Months Ended
Jun. 30, 2026
Retirement Benefits [Abstract]  
Schedule of Net Benefit Costs
Net periodic postretirement benefit credit included the following components:
Three Months Ended June 30,Six Months Ended June 30,
2026202520262025
(Dollars in millions)
Service cost for benefits earned$0.1 $0.1 $0.1 $0.2 
Interest cost on accumulated postretirement benefit obligation1.7 1.9 3.3 3.9 
Expected return on plan assets(0.1)(0.1)(0.1)(0.2)
Amortization of prior service credit(2.9)(10.2)(5.7)(20.4)
Net periodic postretirement benefit credit$(1.2)$(8.3)$(2.4)$(16.5)