Debt Securities (Composition of Debt Securities Portfolio by Credit Rating Agencies) (Narrative) (Detail) - USD ($) $ in Millions	Sep. 30, 2022	Dec. 31, 2021
Schedule Of Available For Sale Securities [Line Items]
Debt securities, Estimated fair value	$ 8,153	$ 9,362
Estimated fair value of debt securities, Unrealized loss position	7,944	$ 5,772
Bank Loans
Schedule Of Available For Sale Securities [Line Items]
Debt securities, Estimated fair value	151
Estimated fair value of debt securities, Unrealized loss position	146
Emerging Market Securities
Schedule Of Available For Sale Securities [Line Items]
Debt securities, Estimated fair value	64
Estimated fair value of debt securities, Unrealized loss position	64
Non-Investment Grade
Schedule Of Available For Sale Securities [Line Items]
Debt securities, Estimated fair value	213
Estimated fair value of debt securities, Unrealized loss position	208
Non-Investment Grade | Bank Loans
Schedule Of Available For Sale Securities [Line Items]
Debt securities, Estimated fair value	147
Estimated fair value of debt securities, Unrealized loss position	142
Non-Investment Grade | High Yield Corporate Debt Securities
Schedule Of Available For Sale Securities [Line Items]
Debt securities, Estimated fair value	57
Estimated fair value of debt securities, Unrealized loss position	57
Non-Investment Grade | Emerging Market Securities
Schedule Of Available For Sale Securities [Line Items]
Debt securities, Estimated fair value	9
Estimated fair value of debt securities, Unrealized loss position	$ 9