Annual report pursuant to Section 13 and 15(d)

COMPANY-SPONSORED EMPLOYEE BENEFIT PLANS - Net Periodic Benefit Cost for Company Sponsored Pension and Postretirement Benefit Plans (Detail)

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COMPANY-SPONSORED EMPLOYEE BENEFIT PLANS - Net Periodic Benefit Cost for Company Sponsored Pension and Postretirement Benefit Plans (Detail) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Pension Benefits | United States      
Net Periodic Benefit Cost:      
Service cost $ 1,853 $ 1,439 $ 1,661
Interest cost 1,977 2,067 1,799
Expected return on plan assets (3,549) (3,130) (3,201)
Amortization of:      
Amortization of prior service cost 218 218 193
Actuarial (gain) loss 6,211 2,296 1,603
Defined Benefit Plan, Benefit Obligation, (Increase) Decrease for Curtailment 0 0 0
Net periodic benefit cost 6,710 2,890 2,055
Pension Benefits | International Pension Benefits      
Net Periodic Benefit Cost:      
Service cost 67 57 62
Interest cost 40 47 45
Expected return on plan assets (86) (76) (77)
Amortization of:      
Amortization of prior service cost 2 2 1
Actuarial (gain) loss 27 54 24
Defined Benefit Plan, Benefit Obligation, (Increase) Decrease for Curtailment 0 0 0
Net periodic benefit cost 50 84 55
Postemployment Retirement Benefits | United States      
Net Periodic Benefit Cost:      
Service cost 29 23 29
Interest cost 91 108 104
Expected return on plan assets (8) (8) (8)
Amortization of:      
Amortization of prior service cost 7 7 7
Actuarial (gain) loss 246 37 0
Defined Benefit Plan, Benefit Obligation, (Increase) Decrease for Curtailment 0 0 0
Net periodic benefit cost $ 365 $ 167 $ 132