Financial Information by Segment - Financial Information by Reportable Segment (Parenthetical) (Detail) - USD ($) $ in Millions	3 Months Ended
Dec. 31, 2023	Dec. 31, 2022
Segment Reporting Information [Line Items]
Revenues from external customers	$ 958	$ 965

Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss).

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+ Details