v3.20.4
Pension and Postretirement Benefit Plans and Defined Contribution Plans - Analysis of Changes in Significant Investments Valued Using Significant Unobservable Inputs (Details) - Pension Plan [Member] - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Level 3 [Member] | Other Funds [Member]    
Actual return on plan assets:    
Transfer into/(out of) Level 3 $ (2) $ 0
International [Member]    
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]    
Fair value, beginning 8,956 8,215
Actual return on plan assets:    
Exchange rate changes 462 42
Fair value, ending 9,811 8,956
International [Member] | Insurance Contracts [Member]    
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]    
Fair value, beginning 1,027  
Actual return on plan assets:    
Fair value, ending 1,027 1,027
International [Member] | Other Funds [Member]    
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]    
Fair value, beginning [1] 1,524  
Actual return on plan assets:    
Fair value, ending [1] 1,514 1,524
International [Member] | Level 3 [Member]    
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]    
Fair value, beginning 1,342  
Actual return on plan assets:    
Fair value, ending 1,362 1,342
International [Member] | Level 3 [Member] | Insurance Contracts [Member]    
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]    
Fair value, beginning 944 684
Actual return on plan assets:    
Assets held, ending 32 50
Purchases, sales, and settlements, net (38) (40)
Transfer into/(out of) Level 3 (11) 247
Exchange rate changes 42 2
Fair value, ending 969 944
International [Member] | Level 3 [Member] | Other Funds [Member]    
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]    
Fair value, beginning 398 [1] 382
Actual return on plan assets:    
Assets held, ending (10) 6
Purchases, sales, and settlements, net (10) 6
Exchange rate changes 16 4
Fair value, ending [1] $ 393 $ 398
[1] Mostly includes investments in hedge funds and real estate.