United Parcel Service, Inc. Quarterly report [Sections 13 or 15(d)]

EMPLOYEE BENEFIT PLANS - Narrative (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2026	Dec. 31, 2025
Defined Benefit Plan Disclosure [Line Items]
Multiemployer plans, payment term	37 years
Defined Benefit Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Multi-employer plans, withdrawal obligation, fair value	$ 645	$ 662
Defined Benefit Pension Plan \| Long term debt
Defined Benefit Plan Disclosure [Line Items]
Multiemployer plans, withdrawal obligation, present value	792	795
Defined Benefit Pension Plan \| Other current liabilities
Defined Benefit Plan Disclosure [Line Items]
Multiemployer plans, withdrawal obligation, present value	9	$ 9
U.S \| Defined Benefit Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Amount contributed to company- sponsored benefit plans	12
Estimated future employer contributions to defined benefit plan, current fiscal year	1,100
U.S \| U.S. Postretirement Medical Benefits
Defined Benefit Plan Disclosure [Line Items]
Amount contributed to company- sponsored benefit plans	67
Estimated future employer contributions to defined benefit plan, current fiscal year	$ 120