Variable Interest Entities (Narrative) (Detail) - Variable Interest Entity, Primary Beneficiary [Member] $ in Millions	3 Months Ended
	Dec. 31, 2023 VariableInterestEntities	Sep. 30, 2023 USD ($) VariableInterestEntities	Jun. 30, 2023 USD ($) VariableInterestEntities	Mar. 31, 2023 USD ($) VariableInterestEntities	Sep. 30, 2022 USD ($) VariableInterestEntities
Variable Interest Entity [Line Items]
Gains (losses) on the consolidation and deconsolidation | $					$ 0
Structured Finance and International Insurance [Member]
Variable Interest Entity [Line Items]
Number of variable interest entities deconsolidated | VariableInterestEntities	0	1	1	1	1
Number of variable interest entities consolidated | VariableInterestEntities	0				1
Structured Finance and International Insurance [Member] | Recorded Due To Credit Losses in AOCI [Member]
Variable Interest Entity [Line Items]
Net realized gains (losses) related to deconsolidation | $		$ (7)	$ (7)	$ (15)