Significant Accounting Policies - New Accounting Pronouncements Recently Adopted (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022	Jan. 01, 2021
Significant Accounting Policies [Line Items]
Reduction to accumulated other comprehensive income (loss)	$ 297	$ 1,264
Adoption of new accounting standard, adjustment
Significant Accounting Policies [Line Items]
Reduction to accumulated other comprehensive income (loss)		$ (201)
Accounting Standards Update 2018-12 | Adoption of new accounting standard, adjustment
Significant Accounting Policies [Line Items]
Liability for future policy benefits			$ 986
Reduction to accumulated other comprehensive income (loss), before tax			986
Liability for future policy benefits, after tax			766
Reduction to accumulated other comprehensive income (loss)			$ 766