Investments - Equity Securities At Fair Value (Detail) - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022
Debt and Equity Securities, FV-NI [Line Items]
Equity securities, at fair value	$ 13,742	$ 14,892
Corporate and Real estate
Debt and Equity Securities, FV-NI [Line Items]
Percentage of investment in equity securities	100.00%	100.00%
Corporate
Debt and Equity Securities, FV-NI [Line Items]
Percentage of investment in equity securities	72.00%	71.00%
Real estate
Debt and Equity Securities, FV-NI [Line Items]
Percentage of investment in equity securities	28.00%	29.00%
Public and Private equity
Debt and Equity Securities, FV-NI [Line Items]
Percentage of investment in equity securities	100.00%	100.00%
Public equity
Debt and Equity Securities, FV-NI [Line Items]
Percentage of investment in equity securities	9.00%	13.00%
Private equity
Debt and Equity Securities, FV-NI [Line Items]
Percentage of investment in equity securities	91.00%	87.00%