Consolidated Statements of Comprehensive Income (Parenthetical) - USD ($) $ in Millions	12 Months Ended
Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Statement of Comprehensive Income [Abstract]
Net of tax	$ 1	$ 3	$ 8

Amount of tax expense (benefit) allocated to other comprehensive income (loss).

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Section 45
-Paragraph 12
-SubTopic 10
-Topic 220
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482790/220-10-45-12

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 220
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 4
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482765/220-10-50-4

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 830
-SubTopic 30
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481674/830-30-50-1

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 830
-SubTopic 30
-Name Accounting Standards Codification
-Section 45
-Paragraph 17
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481694/830-30-45-17

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 830
-SubTopic 30
-Name Accounting Standards Codification
-Section 45
-Paragraph 20
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481694/830-30-45-20

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04(19))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483586/944-220-S99-1

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 10
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482685/740-10-50-10

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 20
-Name Accounting Standards Codification
-Section 45
-Paragraph 11
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482659/740-20-45-11

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 220
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(21))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483621/220-10-S99-2

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 942
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04(23))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483589/942-220-S99-1

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 20
-Name Accounting Standards Codification
-Section 45
-Paragraph 2
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482659/740-20-45-2

+ Details