Goodwill and Other Intangible Assets - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Mar. 31, 2024	Mar. 31, 2023	Sep. 30, 2023
Goodwill [Line Items]
Goodwill, impairment loss	$ 230		$ 230
Goodwill	17,757		17,757		$ 17,936
Amortization of intangible assets	125	$ 104	247	$ 208
Reporting Unit With Current Year Impairment
Goodwill [Line Items]
Goodwill	$ 215		$ 215