Annual report pursuant to Section 13 and 15(d)

COMPANY-SPONSORED EMPLOYEE BENEFIT PLANS - Additional Information (Details)

v3.24.0.1
COMPANY-SPONSORED EMPLOYEE BENEFIT PLANS - Additional Information (Details) - USD ($)
 1 Months Ended 3 Months Ended 12 Months Ended
Apr. 30, 2021
Jan. 31, 2023
Mar. 31, 2021
Dec. 31, 2023
Dec. 31, 2022
Dec. 31, 2021
Defined Benefit Plan Disclosure [Line Items]            
Wage and benefit rate increase agreement, period       5 years    
Actuarial gain (loss) $ 2,100,000,000     $ (2,400,000,000) $ 20,900,000,000  
Defined benefit plan, immediate recognition of prior service cost (credit)           $ 69,000,000
Defined benefit plan, immediate recognition of prior service cost (credit), after tax           52,000,000
Defined benefit plan, immediate recognition of (gain) loss on plan amendment           66,000,000
Defined benefit plan, immediate recognition of (gain) loss on plan amendment, after tax           50,000,000
Curtailments and settlements of benefit obligations         $ 34,000,000  
Defined Benefit Plan, Net Periodic Benefit (Cost) Credit, Settlement and Curtailment Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]         Investment income and other  
Curtailment of benefit obligation, after tax         $ 24,000,000  
Pension and postretirement benefit (income) expense       $ 1,330,000,000 (129,000,000) (2,456,000,000)
Government Assistance, Statement of Income or Comprehensive Income [Extensible Enumeration], Not Disclosed Flag   American Rescue Plan Act        
Health care cost trends, initial annual rate increase       7.25%    
Health care cost trends, an ultimate trend rate       4.50%    
Employer contributions       $ 1,393,000,000 2,342,000,000 $ 576,000,000
Defined benefit plan, actuarial gain (loss), discount rates       $ (2,300,000,000) $ 21,100,000,000  
Service cost discount rate       5.40% 5.77% 3.11%
Defined benefit plan, actuarial gain (loss), demographic and assumption changes       $ (100,000,000) $ (200,000,000)  
Common stock held in plan assets (in shares)       0 0  
American Rescue Plan Act Remeasurement Adjustment            
Defined Benefit Plan Disclosure [Line Items]            
Accumulated other comprehensive income     $ 3,100,000,000      
Unusual or infrequent item, net (gain) loss     3,300,000,000      
Hedge Funds            
Defined Benefit Plan Disclosure [Line Items]            
Unfunded commitments to limited partnerships       $ 0    
Private Equity and Real Estate            
Defined Benefit Plan Disclosure [Line Items]            
Unfunded commitments to limited partnerships       3,300,000,000    
Central States Pension Fund            
Defined Benefit Plan Disclosure [Line Items]            
Government assistance, amount   $ 35,800,000,000        
Pension Benefits            
Defined Benefit Plan Disclosure [Line Items]            
Accumulated benefit obligation for pension plans       49,200,000,000 $ 44,800,000,000  
Employer contributions       35,000,000 31,000,000  
Postemployment Retirement Benefits            
Defined Benefit Plan Disclosure [Line Items]            
Accumulated benefit obligation for pension plans       2,000,000,000.0 2,000,000,000.0  
Postretirement Medical Benefits            
Defined Benefit Plan Disclosure [Line Items]            
Employer contributions       $ 51,000,000 174,000,000  
Minimum            
Defined Benefit Plan Disclosure [Line Items]            
Duration for unfunded commitments to be contributed       3 years    
Minimum | Private Equity and Real Estate            
Defined Benefit Plan Disclosure [Line Items]            
Redemption notice period, lower limit       10 years    
Minimum | U.S. Pension Benefits            
Defined Benefit Plan Disclosure [Line Items]            
Postretirement medical plans service minimum eligibility year       10 years    
Postretirement medical plans service minimum eligibility age       55 years    
Maximum            
Defined Benefit Plan Disclosure [Line Items]            
Duration for unfunded commitments to be contributed       6 years    
Maximum | Private Equity and Real Estate            
Defined Benefit Plan Disclosure [Line Items]            
Redemption notice period, upper limit       15 years    
UPS/IBT Plan            
Defined Benefit Plan Disclosure [Line Items]            
Reclassification to earnings, before tax           $ 3,300,000,000
Impact on net income           2,500,000,000
Defined benefit plan, actuarial gain (loss), immediate recognition as component in net periodic benefit (cost) credit     6,400,000,000      
Defined benefit plan, reduction of liability for coordinating benefits     5,100,000,000      
Defined benefit plan, actuarial gain (loss), other actuarial assumptions     $ 1,300,000,000      
Employee Defined Contribution Plans            
Defined Benefit Plan Disclosure [Line Items]            
Contributions charged to expense       $ 161,000,000 153,000,000 153,000,000
UPS 401(k) Savings Plan            
Defined Benefit Plan Disclosure [Line Items]            
Contributions charged to expense       380,000,000 83,000,000 107,000,000
Transition contributions       $ 128,000,000 $ 0 0
UPS 401(k) Savings Plan | Minimum            
Defined Benefit Plan Disclosure [Line Items]            
Employer contribution, percent of eligible compensation       5.00% 3.00%  
UPS 401(k) Savings Plan | Maximum            
Defined Benefit Plan Disclosure [Line Items]            
Employer contribution, percent of eligible compensation       8.00% 8.00%  
Defined Contribution Money Purchase Plans            
Defined Benefit Plan Disclosure [Line Items]            
Contributions charged to expense       $ 132,000,000 $ 119,000,000 $ 112,000,000