XML 47 R34.htm IDEA: XBRL DOCUMENT v3.24.2.u1
Pension and Postretirement Benefit Costs (Tables)
 6 Months Ended
Jun. 30, 2024
Retirement Benefits [Abstract]  
Schedule of Net Benefit Costs
Net periodic pension cost included the following components:
Three Months Ended June 30,Six Months Ended June 30,
2024202320242023
 (Dollars in millions)
Interest cost on projected benefit obligation$1.6 $7.4 $3.2 $14.8 
Expected return on plan assets(1.2)(6.6)(2.4)(13.2)
Net periodic pension cost$0.4 $0.8 $0.8 $1.6 
Net periodic postretirement benefit credit included the following components:
Three Months Ended June 30,Six Months Ended June 30,
2024202320242023
 (Dollars in millions)
Service cost for benefits earned$0.1 $0.2 $0.2 $0.3 
Interest cost on accumulated postretirement benefit obligation2.3 2.5 4.6 5.0 
Expected return on plan assets(0.1)(0.2)(0.2)(0.3)
Amortization of prior service credit(13.3)(13.4)(26.5)(26.8)
Net periodic postretirement benefit credit$(11.0)$(10.9)$(21.9)$(21.8)