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

EMPLOYEE BENEFIT PLANS - Narrative (Details) - USD ($) $ in Millions	1 Months Ended	9 Months Ended
	Aug. 31, 2026	Sep. 30, 2026	Sep. 30, 2025	Dec. 31, 2025
Defined Benefit Plan Disclosure [Line Items]
Pension contribution funded through debt issuance	$ 450	$ 450	$ 0
Multiemployer plans, payment term		36 years
Defined Benefit Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Multi-employer plans, withdrawal obligation, fair value		$ 589		$ 662
Defined Benefit Pension Plan \| Balance Sheet Location [Axis]: us-gaap:OtherLiabilitiesCurrent
Defined Benefit Plan Disclosure [Line Items]
Multiemployer plans, withdrawal obligation, present value		10		9
Defined Benefit Pension Plan \| Balance Sheet Location [Axis]: us-gaap:OtherLiabilitiesNoncurrent
Defined Benefit Plan Disclosure [Line Items]
Multiemployer plans, withdrawal obligation, present value		788		$ 795
U.S \| Defined Benefit Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Amount contributed to company- sponsored benefit plans		1,100
U.S \| U.S. Postretirement Medical Benefits
Defined Benefit Plan Disclosure [Line Items]
Amount contributed to company- sponsored benefit plans		$ 229