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Pension Plan and Other Postretirement Benefits (Tables)
 3 Months Ended
Mar. 31, 2024
Retirement Benefits [Abstract]  
Schedule of components of net periodic benefit costs for the pension plans and other postretirement benefits
The following table lists components of net periodic benefit costs for the pension plans and other postretirement benefits. The data listed under “pension plan” includes the qualified pension plan and the non-qualified SERP. The data listed under “other benefits” is for all other postretirement benefits.
 Three Months Ended March 31,
 Pension PlanOther Benefits
 2024202320242023
Service cost$5,648 $6,046 $1,520 $1,126 
Interest cost8,881 8,746 1,684 1,297 
Expected return on plan assets(13,236)(13,421)(2,987)(2,636)
Amortization of prior service cost131 131 39 39 
Recognized net actuarial (gain) loss189 (637)(198)(581)
Net periodic benefit cost (credit)$1,613 $865 $58 $(755)