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Employee Benefit Plans
 3 Months Ended
Mar. 31, 2021
Compensation And Retirement Disclosure [Abstract]  
Employee Benefit Plans

8. Employee Benefit Plans

The components of net periodic cost for our defined benefit pension plan and for our postretirement benefit plan are included in the following tables:

 

 

 

Three Months Ended March 31,

 

 

 

2021

 

 

2020

 

Net Periodic Pension Cost

 

(Dollars in millions)

 

Interest cost

 

$

1.7

 

 

$

3.2

 

Actuarial loss amortization

 

 

4.3

 

 

 

3.9

 

Less: Expected return on plan assets

 

 

(3.3

)

 

 

(5.7

)

Net periodic pension cost

 

$

2.7

 

 

$

1.4

 

 

 

 

Three Months Ended March 31,

 

 

 

2021

 

 

2020

 

Net Periodic Postretirement Benefit

 

(Dollars in millions)

 

Interest cost

 

$

—

 

 

$

0.1

 

Actuarial gain amortization

 

 

(0.5

)

 

 

(0.6

)

Prior service credit amortization

 

 

—

 

 

 

(0.1

)

Net periodic postretirement benefit gain

 

$

(0.5

)

 

$

(0.6

)