Related Party Transactions (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
Related Party Transaction [Line Items]
Net sales to related parties	$ 14,535	$ 14,688	$ 15,395
Purchases from related parties	13,574	13,760	14,362
Accounts receivable due from related parties	1,873	1,896
Accounts payable due to related parties	2,549	2,552
Related Party
Related Party Transaction [Line Items]
Net sales to related parties	148	251	253
Purchases from related parties	311	399	$ 397
Accounts receivable due from related parties	16	28
Accounts payable due to related parties	$ 58	$ 114