Investments - Narrative (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Jun. 30, 2026	Jun. 30, 2026	Jun. 30, 2025	Sep. 30, 2025
Investments, Debt and Equity Securities [Abstract]
Cumulative upward adjustments from observed price	$ 23	$ 23		$ 23
Cumulative downward adjustments from impairments	17	17		$ 10
Unrealized losses on investments	$ 7	$ 7	$ 3

Amount of cumulative loss from downward price adjustment on investment in equity security without readily determinable fair value.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 321
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479536/321-10-50-3

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- Definition

Amount of cumulative gain from upward price adjustment on investment in equity security without readily determinable fair value.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 321
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479536/321-10-50-3

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- References

No definition available.

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- Definition

Amount of unrealized gain (loss) on investment.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Section 45
-Paragraph 28
-Subparagraph (b)
-SubTopic 10
-Topic 230
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482740/230-10-45-28

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