Stockholders' Equity - Number of Shares of Class A Common Shares Outstanding on an As-Converted Basis (Details) shares in Millions	Mar. 31, 2024 shares	Sep. 30, 2023 shares
Schedule of Common Stock as Converted [Line Items]
Preferred stock, shares outstanding (in shares)	5	5
As-converted Class A Common Stock (in shares)	2,025	2,047
Series A preferred stock
Schedule of Common Stock as Converted [Line Items]
Preferred stock, shares outstanding (in shares)	0	0
Preferred stock, conversion rate into Class A Common Stock	100.0000	100.0000
As-converted Class A Common Stock (in shares)	6	7
Series B preferred stock
Schedule of Common Stock as Converted [Line Items]
Preferred stock, shares outstanding (in shares)	2	2
Preferred stock, conversion rate into Class A Common Stock	2.9030	2.9370
As-converted Class A Common Stock (in shares)	7	7
Series C preferred stock
Schedule of Common Stock as Converted [Line Items]
Preferred stock, shares outstanding (in shares)	3	3
Preferred stock, conversion rate into Class A Common Stock	3.6250	3.6290
As-converted Class A Common Stock (in shares)	11	11
Class A common stock
Schedule of Common Stock as Converted [Line Items]
Common stock, shares outstanding (in shares)	1,574	1,594
As-converted Class A Common Stock (in shares)	1,574	1,594
Class B-1 common stock
Schedule of Common Stock as Converted [Line Items]
Common stock, shares outstanding (in shares)	245	245
Common stock, conversion rate into Class A Common Stock	1.5875	1.5875
As-converted Class A Common Stock (in shares)	390	390
Class C common stock
Schedule of Common Stock as Converted [Line Items]
Common stock, shares outstanding (in shares)	9	10
Common stock, conversion rate into Class A Common Stock	4.0000	4.0000
As-converted Class A Common Stock (in shares)	37	38