Quarterly report pursuant to Section 13 or 15(d)

EMPLOYEE BENEFIT PLANS - Additional Information (Detail)

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EMPLOYEE BENEFIT PLANS - Additional Information (Detail)
$ in Millions
 3 Months Ended 12 Months Ended
Dec. 31, 2007
USD ($)
Mar. 31, 2021
USD ($)
Dec. 31, 2020
USD ($)
employee
Defined Benefit Plan Disclosure [Line Items]      
Multiemployer Plans, Payment Term   42 years  
National Master Agreement And Various Supplemental Agreements      
Defined Benefit Plan Disclosure [Line Items]      
Number of employees covered | employee     327,000
National Master Agreement And Various Supplemental Agreements | UPS Freight      
Defined Benefit Plan Disclosure [Line Items]      
Number of employees covered | employee     11,000
Independent Pilots Association      
Defined Benefit Plan Disclosure [Line Items]      
Number of employees covered | employee     3,000
Teamsters Local 2727      
Defined Benefit Plan Disclosure [Line Items]      
Number of employees covered | employee     1,600
International Association Of Machinists And Aerospace Workers      
Defined Benefit Plan Disclosure [Line Items]      
Number of employees covered | employee     3,400
UPS/IBT Plan      
Defined Benefit Plan Disclosure [Line Items]      
Actuarial gain   $ 6,400  
Reduction of the liability for coordinating benefits   5,100  
Gain from other updated actuarial assumptions   1,300  
Benefit from basis point increase in discount rate   $ 1,600  
Basis point increase   0.72%  
Asset loss resulting from actual asset returns   $ 300  
Basis points below expected return   2.20%  
Actuarial gain recorded in accumulated other comprehensive income   $ 3,100  
Pre-tax actuarial gain   3,300  
Actuarial gain, after tax   2,500  
Defined Benefit Pension Plan      
Defined Benefit Plan Disclosure [Line Items]      
Multi-employer Plans, Withdrawal Obligation, Fair Value Disclosure   916 $ 1,000
Defined Benefit Pension Plan | Central States Pension Fund      
Defined Benefit Plan Disclosure [Line Items]      
Payment of withdrawal liability $ 6,100    
Pension liability     5,500
Defined Benefit Pension Plan | Long term debt      
Defined Benefit Plan Disclosure [Line Items]      
Multiemployer Plans, Withdrawal Obligation, Present Value   835 837
Defined Benefit Pension Plan | Other current liabilities      
Defined Benefit Plan Disclosure [Line Items]      
Multiemployer Plans, Withdrawal Obligation, Present Value   8 $ 7
Defined Benefit Pension Plan | U.S. Pension Benefits      
Defined Benefit Plan Disclosure [Line Items]      
Amount contributed to company- sponsored benefit plans   22  
Estimated future employer contributions to defined benefit plan, current fiscal year   72,000  
U.S. Postretirement Medical Benefits | U.S. Pension Benefits      
Defined Benefit Plan Disclosure [Line Items]      
Amount contributed to company- sponsored benefit plans   193  
Estimated future employer contributions to defined benefit plan, current fiscal year   $ 63,000