Investments - Equity Securities At Fair Value (Detail) - USD ($) $ in Millions	Sep. 30, 2022	Dec. 31, 2021
Debt and Equity Securities, FV-NI [Line Items]
Equity securities, at fair value	$ 15,359	$ 18,937
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	73.00%	78.00%
Real estate
Debt and Equity Securities, FV-NI [Line Items]
Percentage of investment in equity securities	27.00%	22.00%
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	17.00%	24.00%
Private equity
Debt and Equity Securities, FV-NI [Line Items]
Percentage of investment in equity securities	83.00%	76.00%