Annual report pursuant to Section 13 and 15(d)

COMPANY-SPONSORED EMPLOYEE BENEFIT PLANS - Projected Benefit Obligation, Accumulated Benefit Obligation, and Fair Value of Plan Assets for Pension Plans With an Accumulated Benefit Obligation in Excess of Plan Assets (Detail)

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COMPANY-SPONSORED EMPLOYEE BENEFIT PLANS - Projected Benefit Obligation, Accumulated Benefit Obligation, and Fair Value of Plan Assets for Pension Plans With an Accumulated Benefit Obligation in Excess of Plan Assets (Detail) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss) $ (10,100) $ (8,000)  
Fair value of plan assets at beginning of year 47,767    
Fair value of plan assets at end of year 54,881 47,767  
United States      
Defined Benefit Plan Disclosure [Line Items]      
Fair value of plan assets at beginning of year 46,209    
Fair value of plan assets at end of year 53,046 46,209  
International Pension Benefits      
Defined Benefit Plan Disclosure [Line Items]      
Fair value of plan assets at beginning of year 1,558    
Fair value of plan assets at end of year 1,835 1,558  
Pension Benefits | United States      
Defined Benefit Plan Disclosure [Line Items]      
Projected benefit obligation, Projected Benefit Obligation Exceeds the Fair Value of the Plan Assets 65,922 54,039  
Accumulated benefit obligation, Projected Benefit Obligation Exceeds the Fair Value of the Plan Assets 64,937 53,194  
Defined Benefit Plan, Pension Plan with Projected Benefit Obligation in Excess of Plan Assets, Plan Assets 52,997 46,172  
Projected benefit obligation, Accumulated Benefit Obligation Exceeds the Fair Value of Plan Assets 65,922 54,039  
Accumulated benefit obligation, Accumulated Benefit Obligation Exceeds the Fair Value of Plan Assets 64,937 53,194  
Fair value of plan assets, Accumulated Benefit Obligation Exceeds the Fair Value of Plan Assets 52,997 46,172  
Projected benefit obligation at beginning of year 54,039 45,333  
Service cost 1,853 1,439 $ 1,661
Interest cost 1,977 2,067 1,799
Gross benefits paid (1,846) (2,394)  
Plan participants’ contributions 0 0  
Defined Benefit Plan, Benefit Obligation, Increase (Decrease) for Plan Amendment 171 0  
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss) (9,728) (7,594)  
Defined Benefit Plan, Benefit Obligation, Foreign Currency Translation Gain (Loss) 0 0  
Defined Benefit Plan, Plan Assets Level 3 Reconciliation, Increase (Decrease) for Purchase, Sale, and Settlement 0 0  
Defined Benefit Plan Other Benefit Obligations 0 0  
Projected benefit obligation at end of year 65,922 54,039 45,333
Fair value of plan assets at beginning of year 46,172 39,554  
Defined Benefit Plan, Plan Assets, Increase (Decrease) for Actual Return (Loss) 5,878 6,991  
Defined Benefit Plan, Plan Assets, Contributions by Employer 2,793 2,021  
Gross benefits paid (1,846) (2,394)  
Plan participants’ contributions 0 0  
Defined Benefit Plan, Plan Assets, Foreign Currency Translation Gain (Loss) 0 0  
Defined Benefit Plan, Plan Assets, Payment for Settlement 0 0  
Fair value of plan assets at end of year 52,997 46,172 39,554
Increase (Decrease) in Defined Benefit Plan Other Fair Value Of Plan Assets 0 0  
Pension Benefits | International Pension Benefits      
Defined Benefit Plan Disclosure [Line Items]      
Projected benefit obligation, Projected Benefit Obligation Exceeds the Fair Value of the Plan Assets 845 1,319  
Accumulated benefit obligation, Projected Benefit Obligation Exceeds the Fair Value of the Plan Assets 728 1,210  
Defined Benefit Plan, Pension Plan with Projected Benefit Obligation in Excess of Plan Assets, Plan Assets 452 948  
Projected benefit obligation, Accumulated Benefit Obligation Exceeds the Fair Value of Plan Assets 845 1,319  
Accumulated benefit obligation, Accumulated Benefit Obligation Exceeds the Fair Value of Plan Assets 728 1,210  
Fair value of plan assets, Accumulated Benefit Obligation Exceeds the Fair Value of Plan Assets 452 948  
Projected benefit obligation at beginning of year 1,906 1,552  
Service cost 67 57 62
Interest cost 40 47 45
Gross benefits paid (38) (40)  
Plan participants’ contributions 3 3  
Defined Benefit Plan, Benefit Obligation, Increase (Decrease) for Plan Amendment 1 1  
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss) (123) (213)  
Defined Benefit Plan, Benefit Obligation, Foreign Currency Translation Gain (Loss) 80 47  
Defined Benefit Plan, Plan Assets Level 3 Reconciliation, Increase (Decrease) for Purchase, Sale, and Settlement 6 2  
Defined Benefit Plan Other Benefit Obligations 1 28  
Projected benefit obligation at end of year 2,177 1,906 1,552
Fair value of plan assets at beginning of year 1,558 1,284  
Defined Benefit Plan, Plan Assets, Increase (Decrease) for Actual Return (Loss) 184 171  
Defined Benefit Plan, Plan Assets, Contributions by Employer 69 67  
Gross benefits paid (38) (40)  
Plan participants’ contributions 3 3  
Defined Benefit Plan, Plan Assets, Foreign Currency Translation Gain (Loss) 62 49  
Defined Benefit Plan, Plan Assets, Payment for Settlement 3 2  
Fair value of plan assets at end of year 1,835 1,558 1,284
Increase (Decrease) in Defined Benefit Plan Other Fair Value Of Plan Assets 0 (26)  
Postemployment Retirement Benefits | United States      
Defined Benefit Plan Disclosure [Line Items]      
Projected benefit obligation at beginning of year 2,616 2,510  
Service cost 29 23 29
Interest cost 91 108 104
Gross benefits paid (274) (288)  
Plan participants’ contributions 32 30  
Defined Benefit Plan, Benefit Obligation, Increase (Decrease) for Plan Amendment 0 0  
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss) (265) (233)  
Defined Benefit Plan, Benefit Obligation, Foreign Currency Translation Gain (Loss) 0 0  
Defined Benefit Plan, Plan Assets Level 3 Reconciliation, Increase (Decrease) for Purchase, Sale, and Settlement 0 0  
Defined Benefit Plan Other Benefit Obligations 0 0  
Projected benefit obligation at end of year 2,759 2,616 2,510
Fair value of plan assets at beginning of year 37 26  
Defined Benefit Plan, Plan Assets, Increase (Decrease) for Actual Return (Loss) (9) (5)  
Defined Benefit Plan, Plan Assets, Contributions by Employer 263 274  
Gross benefits paid (274) (288)  
Plan participants’ contributions 32 30  
Defined Benefit Plan, Plan Assets, Foreign Currency Translation Gain (Loss) 0 0  
Defined Benefit Plan, Plan Assets, Payment for Settlement 0 0  
Fair value of plan assets at end of year 49 37 $ 26
Increase (Decrease) in Defined Benefit Plan Other Fair Value Of Plan Assets $ 0 $ 0