Annual report pursuant to Section 13 and 15(d)

PENSION AND OTHER POSTRETIREMENT BENEFITS - (Details 5 ) - Level 3 Fair Value Reconciliation

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PENSION AND OTHER POSTRETIREMENT BENEFITS - (Details 5 ) - Level 3 Fair Value Reconciliation - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2021
Dec. 31, 2020
Dec. 31, 2019
UNITED STATES      
Summary of changes in the fair value of level 3 assets      
Fair value of plan assets $ 3,548 $ 3,429 $ 3,357
UNITED STATES | Fair Value, Inputs, Level 3      
Summary of changes in the fair value of level 3 assets      
Fair value of plan assets 551 431 371
Unrealized gains (losses) on assets still held at the reporting date 155 23  
Purchases, sales and settlements, net (35) 37  
UNITED STATES | Fair Value, Inputs, Level 3 | Private Markets      
Summary of changes in the fair value of level 3 assets      
Fair value of plan assets 471 359 299
Unrealized gains (losses) on assets still held at the reporting date 144 21  
Purchases, sales and settlements, net (32) 39  
UNITED STATES | Fair Value, Inputs, Level 3 | Real Assets      
Summary of changes in the fair value of level 3 assets      
Fair value of plan assets 80 72 72
Unrealized gains (losses) on assets still held at the reporting date 11 2  
Purchases, sales and settlements, net (3) (2)  
UNITED KINGDOM      
Summary of changes in the fair value of level 3 assets      
Fair value of plan assets 2,390 2,337 2,010
UNITED KINGDOM | Insurance      
Summary of changes in the fair value of level 3 assets      
Fair value of plan assets 514 556  
UNITED KINGDOM | Fair Value, Inputs, Level 3      
Summary of changes in the fair value of level 3 assets      
Fair value of plan assets 903 838 735
Unrealized gains (losses) on assets still held at the reporting date 74 100  
Purchases, sales and settlements, net (9) 3  
UNITED KINGDOM | Fair Value, Inputs, Level 3 | Private Markets      
Summary of changes in the fair value of level 3 assets      
Fair value of plan assets 356 251 224
Unrealized gains (losses) on assets still held at the reporting date 114 22  
Purchases, sales and settlements, net (9) 5  
UNITED KINGDOM | Fair Value, Inputs, Level 3 | Real Assets      
Summary of changes in the fair value of level 3 assets      
Fair value of plan assets 33 31 35
Unrealized gains (losses) on assets still held at the reporting date 2 (2)  
Purchases, sales and settlements, net 0 (2)  
UNITED KINGDOM | Fair Value, Inputs, Level 3 | Insurance      
Summary of changes in the fair value of level 3 assets      
Fair value of plan assets 514 556 $ 476
Unrealized gains (losses) on assets still held at the reporting date (42) 80  
Purchases, sales and settlements, net $ 0 $ 0