Debt Securities (Composition of Debt Securities Portfolio by Credit Rating Agencies) (Narrative) (Detail) - USD ($) $ in Millions	Mar. 31, 2022	Dec. 31, 2021
Schedule Of Available For Sale Securities [Line Items]
Debt securities, Estimated fair value	$ 8,937	$ 9,362
Bank Loans
Schedule Of Available For Sale Securities [Line Items]
Debt securities, Estimated fair value	162
High Yield Corporate Debt Securities
Schedule Of Available For Sale Securities [Line Items]
Debt securities, Estimated fair value	70
Emerging Market Securities
Schedule Of Available For Sale Securities [Line Items]
Debt securities, Estimated fair value	80
Non-Investment Grade
Schedule Of Available For Sale Securities [Line Items]
Debt securities, Estimated fair value	240
Non-Investment Grade | Bank Loans
Schedule Of Available For Sale Securities [Line Items]
Debt securities, Estimated fair value	157
Non-Investment Grade | Emerging Market Securities
Schedule Of Available For Sale Securities [Line Items]
Debt securities, Estimated fair value	$ 12