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Fair Value Measurements - Narrative (Details) $ in Millions, € in Billions, ¥ in Billions	3 Months Ended		9 Months Ended
	Jun. 30, 2026 USD ($)	Jun. 30, 2025 USD ($)	Jun. 30, 2026 USD ($)	Jun. 30, 2025 USD ($)	Jun. 30, 2026 EUR (€)	Sep. 30, 2025 USD ($)	Sep. 30, 2025 EUR (€)	Sep. 30, 2025 JPY (¥)
Fair Value [Line Items]
Derivative liabilities	$ 74		$ 74			$ 24
Equity securities, unrealized gains	38	$ 24	31	$ 14
Net Investment Hedging
Fair Value [Line Items]
Pre-tax gains (losses) related to net investment hedges recorded in other comprehensive income (loss)	22	$ (269)	115	$ (162)
Foreign currency denominated debt
Fair Value [Line Items]
Derivative, notional amount					€ 2.9		€ 2.9	¥ 30
Foreign currency denominated debt \| Derivatives and Hedging Activities Designated as Hedging Instruments
Fair Value [Line Items]
Derivative liabilities	3,400		3,400			3,600
Quoted Prices in Active Markets (Level 1)
Fair Value [Line Items]
Derivative liabilities	0		0			0
Significant Other Observable Inputs (Level 2)
Fair Value [Line Items]
Derivative liabilities	$ 74		$ 74			$ 24