Fair value portion of debt instrument payable, including, but not limited to, notes payable and loans payable.

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 55
-Paragraph 69C
-URI http://asc.fasb.org/extlink&oid=123466577&loc=SL123495737-112612

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 55
-Paragraph 69B
-URI http://asc.fasb.org/extlink&oid=123466577&loc=SL123495735-112612

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
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-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 1D
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-URI http://asc.fasb.org/extlink&oid=123466505&loc=SL123495340-112611

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

Fair Value Measurements - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Sep. 30, 2021
Fair Value [Line Items]
Fair value of long term debt	$ 8,400		$ 8,500
Fair Value, Inputs, Level 1 [Member]
Fair Value [Line Items]
Fair value of long term debt	8,200		8,300
Fair Value, Inputs, Level 2 [Member]
Fair Value [Line Items]
Fair value of long term debt	200		$ 200
Deferred compensation plan assets [Member]
Fair Value [Line Items]
Unrealized gains (losses)	3	$ 5
Exchange Traded Funds
Fair Value [Line Items]
Unrealized gains (losses)	$ 14	$ 21