Annual report pursuant to Section 13 and 15(d)

PENSIONS AND POSTRETIREMENT BENEFITS - Fair Value Measurements Using Significant Unobservable Inputs (Level 3) on Changes in Plan Assets (Details)

v3.20.4
PENSIONS AND POSTRETIREMENT BENEFITS - Fair Value Measurements Using Significant Unobservable Inputs (Level 3) on Changes in Plan Assets (Details) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Pension Plan [Member]    
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]    
Fair value of plan assets — beginning of year $ 749.0 $ 687.0
Actual return on plan assets:    
Fair value of plan assets — end of year 5,332.0 749.0
Pension Plan [Member] | Private Equity Funds [Member]    
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]    
Fair value of plan assets — beginning of year 50.0  
Actual return on plan assets:    
Fair value of plan assets — end of year 114.0 50.0
Reserve for investment commitments 86.0  
Other Postretirement Benefits Plan [Member]    
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]    
Fair value of plan assets — beginning of year 260.0 240.0
Actual return on plan assets:    
Fair value of plan assets — end of year 783.0 260.0
Other Postretirement Benefits Plan [Member] | Private Equity Funds [Member]    
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]    
Fair value of plan assets — beginning of year 2.0  
Actual return on plan assets:    
Fair value of plan assets — end of year 3.0 2.0
Fair Value, Inputs, Level 3 [Member] | Pension Plan [Member]    
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]    
Fair value of plan assets — beginning of year 212.0 229.0
Actual return on plan assets:    
Relating to assets still held at the reporting date 8.0 (1.0)
Relating to assets sold during the period 6.0 30.0
Purchases 195.0 17.0
Sales (13.0) (60.0)
Acquired through business combinations 262.0  
Other 0.0 (3.0)
Fair value of plan assets — end of year 670.0 212.0
Fair Value, Inputs, Level 3 [Member] | Pension Plan [Member] | Private Equity Funds [Member]    
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]    
Fair value of plan assets — beginning of year 50.0  
Actual return on plan assets:    
Fair value of plan assets — end of year 114.0 50.0
Fair Value, Inputs, Level 3 [Member] | Other Postretirement Benefits Plan [Member]    
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]    
Fair value of plan assets — beginning of year 34.0  
Actual return on plan assets:    
Fair value of plan assets — end of year 38.0 34.0
Fair Value, Inputs, Level 3 [Member] | Other Postretirement Benefits Plan [Member] | Private Equity Funds [Member]    
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]    
Fair value of plan assets — beginning of year 2.0  
Actual return on plan assets:    
Fair value of plan assets — end of year 3.0 2.0
Fair Value, Inputs, Level 3 [Member] | Other Postretirement Benefits Plan [Member] | Veba Trust [Member]    
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]    
Fair value of plan assets — beginning of year 34.0 36.0
Actual return on plan assets:    
Relating to assets still held at the reporting date 2.0 1.0
Relating to assets sold during the period 1.0 0.0
Purchases 0.0 0.0
Sales (1.0) (3.0)
Acquired through business combinations 2.0  
Other 0.0 0.0
Fair value of plan assets — end of year $ 38.0 $ 34.0