XML 124 R94.htm IDEA: XBRL DOCUMENT v3.25.0.1
Postretirement Health Care and Life Insurance Benefits - Fair Value of Plan Assets in Non-Represented Trust by Asset (Details) - USD ($)
$ in Millions
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
Dec. 31, 2021
Other Postretirement Benefits Plan        
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]        
Defined benefit plan, assets $ 11.3 $ 14.3 $ 17.4  
Other Postretirement Benefits Plan | U.S. equity securities        
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]        
Defined benefit plan, assets 2.7 3.0    
Other Postretirement Benefits Plan | International equity securities        
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]        
Defined benefit plan, assets 0.7 0.9    
Other Postretirement Benefits Plan | Corporate bonds        
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]        
Defined benefit plan, assets 3.5 5.2    
Other Postretirement Benefits Plan | U.S. government securities        
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]        
Defined benefit plan, assets 3.8 4.6    
Other Postretirement Benefits Plan | Cash funds        
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]        
Defined benefit plan, assets 0.6 0.6    
Fair Value, Inputs, Level 1 | Other Postretirement Benefits Plan        
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]        
Defined benefit plan, assets 5.1 6.3    
Fair Value, Inputs, Level 1 | Other Postretirement Benefits Plan | U.S. equity securities        
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]        
Defined benefit plan, assets 2.7 3.0    
Fair Value, Inputs, Level 1 | Other Postretirement Benefits Plan | International equity securities        
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]        
Defined benefit plan, assets 0.7 0.9    
Fair Value, Inputs, Level 1 | Other Postretirement Benefits Plan | Corporate bonds        
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]        
Defined benefit plan, assets 0.0 0.0    
Fair Value, Inputs, Level 1 | Other Postretirement Benefits Plan | U.S. government securities        
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]        
Defined benefit plan, assets 1.1 1.8    
Fair Value, Inputs, Level 1 | Other Postretirement Benefits Plan | Cash funds        
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]        
Defined benefit plan, assets 0.6 0.6    
Fair Value, Inputs, Level 2 | Other Postretirement Benefits Plan        
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]        
Defined benefit plan, assets 6.2 8.0    
Fair Value, Inputs, Level 2 | Other Postretirement Benefits Plan | U.S. equity securities        
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]        
Defined benefit plan, assets 0.0 0.0    
Fair Value, Inputs, Level 2 | Other Postretirement Benefits Plan | International equity securities        
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]        
Defined benefit plan, assets 0.0 0.0    
Fair Value, Inputs, Level 2 | Other Postretirement Benefits Plan | Corporate bonds        
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]        
Defined benefit plan, assets 3.5 5.2    
Fair Value, Inputs, Level 2 | Other Postretirement Benefits Plan | U.S. government securities        
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]        
Defined benefit plan, assets 2.7 2.8    
Fair Value, Inputs, Level 2 | Other Postretirement Benefits Plan | Cash funds        
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]        
Defined benefit plan, assets 0.0 0.0    
Fair Value, Inputs, Level 3        
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]        
Defined benefit plan, assets 0.0 0.0 $ 430.4 $ 0.3
Fair Value, Inputs, Level 3 | Other Postretirement Benefits Plan        
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]        
Defined benefit plan, assets 0.0 0.0    
Fair Value, Inputs, Level 3 | Other Postretirement Benefits Plan | U.S. equity securities        
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]        
Defined benefit plan, assets 0.0 0.0    
Fair Value, Inputs, Level 3 | Other Postretirement Benefits Plan | International equity securities        
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]        
Defined benefit plan, assets 0.0 0.0    
Fair Value, Inputs, Level 3 | Other Postretirement Benefits Plan | Corporate bonds        
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]        
Defined benefit plan, assets 0.0 0.0    
Fair Value, Inputs, Level 3 | Other Postretirement Benefits Plan | U.S. government securities        
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]        
Defined benefit plan, assets 0.0 0.0    
Fair Value, Inputs, Level 3 | Other Postretirement Benefits Plan | Cash funds        
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]        
Defined benefit plan, assets $ 0.0 $ 0.0