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Retirement Plans, Weighted-Average Assumption Used to Determine Benefit Obligation (Details)
12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Pension Plan [Member]    
Weighted-average assumption used to determine benefit obligation at end of year [Abstract]    
Discount rate 5.70% [1] 5.10%
Health care cost trend rate [Abstract]    
Initial rate 0.00% 0.00%
Ultimate rate 0.00% 0.00%
Pension Plan [Member] | Minimum [Member]    
Weighted-average assumption used to determine benefit obligation at end of year [Abstract]    
Discount rate [1]   5.10%
Pension Plan [Member] | Maximum [Member]    
Weighted-average assumption used to determine benefit obligation at end of year [Abstract]    
Discount rate [1]   5.20%
SERP [Member]    
Weighted-average assumption used to determine benefit obligation at end of year [Abstract]    
Discount rate [1] 5.70% 5.10%
Rate of compensation increase 0.00% 0.00%
Health care cost trend rate [Abstract]    
Initial rate 0.00% 0.00%
Ultimate rate 0.00% 0.00%
Other Postretirement Benefits [Member]    
Weighted-average assumption used to determine benefit obligation at end of year [Abstract]    
Discount rate [1] 5.70% 5.10%
Rate of compensation increase 0.00% 0.00%
Health care cost trend rate [Abstract]    
Initial rate 6.75% 6.25%
Ultimate rate 5.00% 5.00%
Years to ultimate 2032 2029
Higman Pension Plan [Member]    
Weighted-average assumption used to determine benefit obligation at end of year [Abstract]    
Discount rate 5.70% 5.20%
[1] The 2024 discount rate was 5.7% for both the Kirby Pension Plan and the Higman Pension Plan. The 2023 discount rate was 5.1% for the Kirby Pension Plan and 5.2% for the Higman Pension Plan.