Investments - Reconciliation of Available-for-Sale Securities from Cost Basis to Fair Value (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Debt Securities, Available-for-Sale [Line Items]
Amortized Cost	$ 88,231	$ 110,944
Gross Unrealized Gains	1,054	1,041
Gross Unrealized Losses	6,966	12,499
Allowance for Credit Losses	19	21	$ 19	$ 13
Fair Value	82,300	99,465
Corporate bonds
Debt Securities, Available-for-Sale [Line Items]
Amortized Cost	68,811	88,950
Gross Unrealized Gains	820	763
Gross Unrealized Losses	5,757	10,538
Allowance for Credit Losses	8	9	17	12
Fair Value	63,866	79,166
U.S. government bonds
Debt Securities, Available-for-Sale [Line Items]
Amortized Cost	414	377
Gross Unrealized Gains	7	5
Gross Unrealized Losses	28	31
Allowance for Credit Losses	0	0
Fair Value	393	351
State and municipal bonds
Debt Securities, Available-for-Sale [Line Items]
Amortized Cost	2,675	5,198
Gross Unrealized Gains	97	170
Gross Unrealized Losses	230	483
Allowance for Credit Losses	0	0
Fair Value	2,542	4,885
Foreign government bonds
Debt Securities, Available-for-Sale [Line Items]
Amortized Cost	309	339
Gross Unrealized Gains	15	17
Gross Unrealized Losses	46	45
Allowance for Credit Losses	0	0
Fair Value	278	311
RMBS
Debt Securities, Available-for-Sale [Line Items]
Amortized Cost	1,719	2,025
Gross Unrealized Gains	27	21
Gross Unrealized Losses	138	203
Allowance for Credit Losses	6	7	$ 1	$ 1
Fair Value	1,602	1,836
CMBS
Debt Securities, Available-for-Sale [Line Items]
Amortized Cost	1,520	1,908
Gross Unrealized Gains	5	3
Gross Unrealized Losses	181	244
Allowance for Credit Losses	0	0
Fair Value	1,344	1,667
ABS
Debt Securities, Available-for-Sale [Line Items]
Amortized Cost	12,556	11,791
Gross Unrealized Gains	62	37
Gross Unrealized Losses	571	925
Allowance for Credit Losses	4	4
Fair Value	12,043	10,899
Hybrid and redeemable preferred securities
Debt Securities, Available-for-Sale [Line Items]
Amortized Cost	227	356
Gross Unrealized Gains	21	25
Gross Unrealized Losses	15	30
Allowance for Credit Losses	1	1
Fair Value	$ 232	$ 350

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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