Stockholders' Equity - Effect of VE Territory Covered Losses Through Conversion Rate Adjustments (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Conversion of Stock [Line Items]
Recovery through conversion rate adjustment	$ (6)	$ 0	$ (6)	$ 1
Series B preferred stock
Conversion of Stock [Line Items]
Reduction in equivalent number of class A common stock (in shares)			1	0
Effective price per share (in dollars per share)			$ 270.07	$ 219.12
Recovery through conversion rate adjustment			$ 161	$ 19
Series C preferred stock
Conversion of Stock [Line Items]
Reduction in equivalent number of class A common stock (in shares)			0	0
Effective price per share (in dollars per share)			$ 269.62	$ 215.28
Recovery through conversion rate adjustment			$ 20	$ 11