Investments - Summary of Cost and Carrying Value of Equity and Trading Debt Securities (Detail) - USD ($) $ in Millions	Mar. 31, 2025	Dec. 31, 2024
Schedule of Investments [Line Items]
Total trading debt securities, Cost	$ 1,994	$ 1,847
Total trading debt, Carrying Value	1,964	1,823
Equity securities at FVTNI, Carrying Value	2,208	1,950
Corporate Debt [Member]
Schedule of Investments [Line Items]
Total trading debt securities, Cost	1,298	1,047
Total trading debt, Carrying Value	1,308	1,061
Government Debt [Member]
Schedule of Investments [Line Items]
Total trading debt securities, Cost	387	578
Total trading debt, Carrying Value	368	557
Asset/Mortgage-Backed Debt [Member]
Schedule of Investments [Line Items]
Total trading debt securities, Cost	309	222
Total trading debt, Carrying Value	288	205
Equity Securities [Member]
Schedule of Investments [Line Items]
Equity securities at FVTNI, Cost	2,104	1,843
Equity securities at FVTNI, Carrying Value	$ 2,208	$ 1,950