Leases - Supplemental Cash Flow Information (Details) - USD ($) $ in Millions	12 Months Ended
Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
Right-of-use assets obtained in exchange for lease obligations:
Operating leases (non-cash activity)	$ 96	$ 84	$ 35
Operating cash flows:
Cash paid for amounts included in the measurement of lease liabilities	$ 110	$ 108	$ 108

Amount of cash outflow from operating lease, excluding payments to bring another asset to condition and location necessary for its intended use.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 842
-SubTopic 20
-Name Accounting Standards Codification
-Section 45
-Paragraph 5
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479041/842-20-45-5

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 842
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 4
-Subparagraph (g)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478964/842-20-50-4

Name:	us-gaap_OperatingLeasePayments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration