Earnings Per Share - Schedule of Weighted Average Number of Shares (Details) - shares shares in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2026	Mar. 31, 2025	Mar. 31, 2026	Mar. 31, 2025
Class B-1 common stock
Schedule of Earnings Per Share, Basic and Diluted, by Common Class, Including Two Class Method [Line Items]
Weighted-average as-converted common stock used in income allocation (in shares)	7	8	8	8
Class B-2 common stock
Schedule of Earnings Per Share, Basic and Diluted, by Common Class, Including Two Class Method [Line Items]
Weighted-average as-converted common stock used in income allocation (in shares)	182	186	182	186
Class C common stock
Schedule of Earnings Per Share, Basic and Diluted, by Common Class, Including Two Class Method [Line Items]
Weighted-average as-converted common stock used in income allocation (in shares)	36	37	36	37
Participating securities
Schedule of Earnings Per Share, Basic and Diluted, by Common Class, Including Two Class Method [Line Items]
Weighted-average as-converted common stock used in income allocation (in shares)	16	20	16	21