Investments - Reconciliation of Available-for-Sale Securities from Cost Basis to Fair Value (Details) - USD ($) $ in Millions	Mar. 31, 2025	Dec. 31, 2024	Mar. 31, 2024	Dec. 31, 2023
Debt Securities, Available-for-Sale [Line Items]
Amortized Cost	$ 89,604	$ 88,978
Gross Unrealized Gains	851	754
Gross Unrealized Losses	7,272	7,786
Allowance for Credit Losses	73	46	$ 21	$ 19
Fair Value	83,110	81,900
Corporate bonds
Debt Securities, Available-for-Sale [Line Items]
Amortized Cost	68,038	67,991
Gross Unrealized Gains	628	560
Gross Unrealized Losses	6,344	6,704
Allowance for Credit Losses	23	14	10	8
Fair Value	62,299	61,833
U.S. government bonds
Debt Securities, Available-for-Sale [Line Items]
Amortized Cost	565	427
Gross Unrealized Gains	5	3
Gross Unrealized Losses	33	40
Allowance for Credit Losses	0	0
Fair Value	537	390
State and municipal bonds
Debt Securities, Available-for-Sale [Line Items]
Amortized Cost	2,337	2,391
Gross Unrealized Gains	34	27
Gross Unrealized Losses	249	270
Allowance for Credit Losses	0	0
Fair Value	2,122	2,148
Foreign government bonds
Debt Securities, Available-for-Sale [Line Items]
Amortized Cost	277	277
Gross Unrealized Gains	12	12
Gross Unrealized Losses	54	56
Allowance for Credit Losses	0	0
Fair Value	235	233
RMBS
Debt Securities, Available-for-Sale [Line Items]
Amortized Cost	1,890	1,849
Gross Unrealized Gains	29	23
Gross Unrealized Losses	133	162
Allowance for Credit Losses	6	7	6	6
Fair Value	1,780	1,703
CMBS
Debt Securities, Available-for-Sale [Line Items]
Amortized Cost	1,857	1,713
Gross Unrealized Gains	8	5
Gross Unrealized Losses	119	135
Allowance for Credit Losses	0	0
Fair Value	1,746	1,583
ABS
Debt Securities, Available-for-Sale [Line Items]
Amortized Cost	14,395	14,103
Gross Unrealized Gains	110	99
Gross Unrealized Losses	331	409
Allowance for Credit Losses	43	24	$ 4	$ 4
Fair Value	14,131	13,769
Hybrid and redeemable preferred securities
Debt Securities, Available-for-Sale [Line Items]
Amortized Cost	245	227
Gross Unrealized Gains	25	25
Gross Unrealized Losses	9	10
Allowance for Credit Losses	1	1
Fair Value	$ 260	$ 241

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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