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Pension plans and other postretirement benefits (Tables)
 3 Months Ended
Mar. 31, 2024
Retirement Benefits [Abstract]  
Net Periodic Defined Benefit Cost for Defined Benefit Plans

The Company provides defined pension and other postretirement benefits (including health care and life insurance benefits) to qualified retired employees. Net periodic benefit for defined benefit plans consisted of the following:

 

 

Pension
Benefits

 

 

Other
Postretirement
Benefits

 

 

 

Three Months Ended March 31,

 

(Dollars in millions)

 

2024

 

 

2023

 

 

2024

 

 

2023

 

Service cost

 

$

2

 

 

$

3

 

 

$

—

 

 

$

—

 

Interest cost on projected benefit obligation

 

 

29

 

 

 

29

 

 

 

1

 

 

 

1

 

Expected return on plan assets

 

 

(51

)

 

 

(51

)

 

 

—

 

 

 

—

 

Amortization of net actuarial gain

 

 

—

 

 

 

(1

)

 

 

(1

)

 

 

(1

)

Net periodic benefit

 

$

(20

)

 

$

(20

)

 

$

—

 

 

$

—