Stockholders' Equity - Number of Shares of Class A Common Shares Outstanding on an As-Converted Basis (Details) shares in Millions	Jun. 30, 2025 shares	Sep. 30, 2024 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)	1,945	1,983
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	9
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	0.9960	1.0030
As-converted Class A Common Stock (in shares)	2	2
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	1.7830	1.7860
As-converted Class A Common Stock (in shares)	6	6
Class A common stock
Schedule of Common Stock as Converted [Line Items]
Common stock, shares outstanding (in shares)	1,702	1,733
Common stock, conversion rate into Class A Common Stock	0	0
As-converted Class A Common Stock (in shares)	1,702	1,733
Class B-1 common stock
Schedule of Common Stock as Converted [Line Items]
Common stock, shares outstanding (in shares)	5	5
Common stock, conversion rate into Class A Common Stock	1.5609	1.5653
As-converted Class A Common Stock (in shares)	8	8
Class B-2 common stock
Schedule of Common Stock as Converted [Line Items]
Common stock, shares outstanding (in shares)	120	120
Common stock, conversion rate into Class A Common Stock	1.5342	1.5430
As-converted Class A Common Stock (in shares)	185	186
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)	36	39