Fair Value Measurements and Investments - Schedule of Non-Marketable Equity Securities (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Mar. 31, 2024	Mar. 31, 2023
Fair Value Disclosures [Abstract]
Initial cost basis	$ 710		$ 710
Upward adjustments	909		909
Downward adjustments (including impairment)	(445)		(445)
Carrying amount	1,174		1,174
Upward adjustments	0	$ 2	9	$ 19
Downward adjustments (including impairment)	$ (15)	$ (89)	$ (15)	$ (89)