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)

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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, 2021
Dec. 31, 2020
Pension Plan    
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]    
Fair value of plan assets — beginning of year $ 5,332 $ 749
Actual return on plan assets:    
Fair value of plan assets — end of year 5,606 5,332
Pension Plan | Private equity    
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]    
Fair value of plan assets — beginning of year 114  
Actual return on plan assets:    
Fair value of plan assets — end of year 151 114
Reserve for investment commitments 151  
Other Postretirement Benefits Plan    
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]    
Fair value of plan assets — beginning of year 783 260
Actual return on plan assets:    
Fair value of plan assets — end of year 812 783
Other Postretirement Benefits Plan | Private equity    
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]    
Fair value of plan assets — beginning of year 3  
Actual return on plan assets:    
Fair value of plan assets — end of year 0 3
Significant Unobservable Inputs (Level 3) | Pension Plan    
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]    
Fair value of plan assets — beginning of year 670 212
Actual return on plan assets:    
Relating to assets still held at the reporting date 124 8
Relating to assets sold during the period 8 6
Purchases 142 195
Sales (40) (13)
Acquired through business combinations 0 262
Fair value of plan assets — end of year 904 670
Significant Unobservable Inputs (Level 3) | Pension Plan | Private equity    
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]    
Fair value of plan assets — beginning of year 114  
Actual return on plan assets:    
Fair value of plan assets — end of year 151 114
Significant Unobservable Inputs (Level 3) | Other Postretirement Benefits Plan    
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]    
Fair value of plan assets — beginning of year 38  
Actual return on plan assets:    
Fair value of plan assets — end of year 42 38
Significant Unobservable Inputs (Level 3) | Other Postretirement Benefits Plan | Private equity    
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]    
Fair value of plan assets — beginning of year 3  
Actual return on plan assets:    
Fair value of plan assets — end of year 0 3
Significant Unobservable Inputs (Level 3) | Other Postretirement Benefits Plan | Veba Trust    
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]    
Fair value of plan assets — beginning of year 38 34
Actual return on plan assets:    
Relating to assets still held at the reporting date 6 2
Relating to assets sold during the period 0 1
Purchases 0 0
Sales (2) (1)
Acquired through business combinations   2
Fair value of plan assets — end of year $ 42 $ 38