Earnings Per Share - Basic and Diluted Earnings Per Share (Detail) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Schedule of Earnings Per Share, Basic and Diluted, by Common Class [Line Items]
Income Allocation - Basic	$ 4,890	$ 4,179
Class A common stock
Schedule of Earnings Per Share, Basic and Diluted, by Common Class [Line Items]
Income Allocation - Basic	$ 3,792	$ 3,243
Weighted- Average Shares Outstanding - Basic (in shares)	1,584	1,629
Earnings per Share - Basic (in dollars per share)	$ 2.39	$ 1.99
Income Allocation - Diluted	$ 4,890	$ 4,179
Weighted- Average Shares Outstanding - Diluted (in shares)	2,045	2,102
Earnings per Share - Diluted (in dollars per share)	$ 2.39	$ 1.99
Class B common stock
Schedule of Earnings Per Share, Basic and Diluted, by Common Class [Line Items]
Income Allocation - Basic	$ 933	$ 784
Weighted- Average Shares Outstanding - Basic (in shares)	245	245
Earnings per Share - Basic (in dollars per share)	$ 3.80	$ 3.19
Income Allocation - Diluted	$ 932	$ 784
Weighted- Average Shares Outstanding - Diluted (in shares)	245	245
Earnings per Share - Diluted (in dollars per share)	$ 3.80	$ 3.19
Weighted-average as-converted common stock used in income allocation (in shares)	390	394
Class C common stock
Schedule of Earnings Per Share, Basic and Diluted, by Common Class [Line Items]
Income Allocation - Basic	$ 91	$ 78
Weighted- Average Shares Outstanding - Basic (in shares)	9	10
Earnings per Share - Basic (in dollars per share)	$ 9.58	$ 7.96
Income Allocation - Diluted	$ 91	$ 78
Weighted- Average Shares Outstanding - Diluted (in shares)	9	10
Earnings per Share - Diluted (in dollars per share)	$ 9.57	$ 7.95
Weighted-average as-converted common stock used in income allocation (in shares)	38	39
Participating securities
Schedule of Earnings Per Share, Basic and Diluted, by Common Class [Line Items]
Income Allocation - Basic	$ 74	$ 74
Income Allocation - Diluted	$ 74	$ 74
Series A preferred stock
Schedule of Earnings Per Share, Basic and Diluted, by Common Class [Line Items]
Weighted-average as-converted common stock used in income allocation (in shares)	6	13
Series B preferred stock
Schedule of Earnings Per Share, Basic and Diluted, by Common Class [Line Items]
Weighted-average as-converted common stock used in income allocation (in shares)	7	7
Series C preferred stock
Schedule of Earnings Per Share, Basic and Diluted, by Common Class [Line Items]
Weighted-average as-converted common stock used in income allocation (in shares)	11	11