RETIREMENT MEDICAL PLANS - Retiree Medical Liability Current and Long Term Components (Details) - USD ($) $ in Millions	Sep. 30, 2019	Sep. 30, 2018
Retiree Medical Liability Current And Long Term Components
Long-term — included in retirement benefits	$ 336	$ 262
U.S. Retiree Medical Plan
Retiree Medical Liability Current And Long Term Components
Current — included in compensation and benefits	11	13
Long-term — included in retirement benefits	56	73
Retiree medical liability	$ 67	$ 86

Amount of liability, recognized in statement of financial position, for defined benefit pension and other postretirement plans.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 210
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
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-Section S99
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Name:	us-gaap_PensionAndOtherPostretirementDefinedBenefitPlansLiabilitiesCurrentAndNoncurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant