Description of Business, Accounting Policies, and Supplemental Disclosures - Cash Equivalents and Marketable Securities (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2024	Mar. 31, 2024	Sep. 30, 2023	Dec. 31, 2023
Schedule of Equity Method Investments [Line Items]
Payments to acquire nonmarketable securities	$ 1,300	$ 2,750	$ 1,250
Nonmarketable securities, agreed additional investment	2,700
Equity investments in private companies	989			$ 754
Equity method investments	1,200			614
Fair Value, Inputs, Level 3
Schedule of Equity Method Investments [Line Items]
Estimated fair value of nonmarketable securities	13,800
Equity Warrant | Fair Value, Inputs, Level 2
Schedule of Equity Method Investments [Line Items]
Fair value of warrants	$ 2,700			$ 2,200