Investments - Debt Instruments At Fair Value (Detail) - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022
Debt and Equity Securities, FV-NI [Line Items]
Debt securities, at fair value	$ 13,305	$ 14,075
Corporate debt securities
Debt and Equity Securities, FV-NI [Line Items]
Debt securities, at fair value	9,362	10,098
Securities backed by real estate
Debt and Equity Securities, FV-NI [Line Items]
Debt securities, at fair value	785	1,003
Money market instruments
Debt and Equity Securities, FV-NI [Line Items]
Debt securities, at fair value	896	1,005
Other
Debt and Equity Securities, FV-NI [Line Items]
Debt securities, at fair value	$ 2,262	$ 1,969