Benefit Plans Other Postemployment Benefits (Details) - USD ($) $ in Millions	12 Months Ended
Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019
Other Post-Employment Benefits
Discount rate	1.52%	0.69%	1.68%
Period expense	$ (20)	$ (45)	$ (59)
Payment of Workers Compensation Claims	74	39
Accounts Payable and Accrued Liabilities
Other Post-Employment Benefits
Postemployment Benefits Liability, Current	0	0
Pension and Other Postretirement Defined Benefit Plans, Liabilities, Noncurrent
Other Post-Employment Benefits
Postemployment benefits liability, noncurrent	$ 340	$ 390	$ 419

For a classified balance sheet, the carrying amount as of the balance sheet date of the portion of the obligations recognized for the various benefits provided to former or inactive employees, their beneficiaries, and covered dependents after employment but before retirement that is payable within one year of the balance sheet date.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 712
-SubTopic 10
-Section 25
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=6410138&loc=d3e79691-111665

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.20)
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 712
-SubTopic 10
-Section 25
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=6410138&loc=d3e79708-111665

Name:	us-gaap_PostemploymentBenefitsLiabilityCurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant