Investments - Reconciliation of Available-for-Sale Securities from Cost Basis to Fair Value (Details) - USD ($) $ in Millions	Jun. 30, 2026	Mar. 31, 2026	Dec. 31, 2025	Jun. 30, 2025	Mar. 31, 2025	Dec. 31, 2024
Debt Securities, Available-for-Sale [Line Items]
Amortized Cost	$ 96,311		$ 92,842
Gross Unrealized Gains	811		1,118
Gross Unrealized Losses	6,711		6,264
Allowance for Credit Losses	138	$ 111	110	$ 85	$ 73	$ 46
Fair Value	90,273		87,586
Corporate bonds
Debt Securities, Available-for-Sale [Line Items]
Amortized Cost	68,832		68,479
Gross Unrealized Gains	625		837
Gross Unrealized Losses	5,900		5,540
Allowance for Credit Losses	44	38	53	36	23	14
Fair Value	63,513		63,723
U.S. government bonds
Debt Securities, Available-for-Sale [Line Items]
Amortized Cost	999		890
Gross Unrealized Gains	3		9
Gross Unrealized Losses	41		32
Allowance for Credit Losses	0		0
Fair Value	961		867
State and municipal bonds
Debt Securities, Available-for-Sale [Line Items]
Amortized Cost	2,120		2,161
Gross Unrealized Gains	26		35
Gross Unrealized Losses	231		231
Allowance for Credit Losses	0		0
Fair Value	1,915		1,965
Foreign government bonds
Debt Securities, Available-for-Sale [Line Items]
Amortized Cost	238		256
Gross Unrealized Gains	15		17
Gross Unrealized Losses	50		50
Allowance for Credit Losses	0		0
Fair Value	203		223
RMBS
Debt Securities, Available-for-Sale [Line Items]
Amortized Cost	1,941		2,034
Gross Unrealized Gains	37		45
Gross Unrealized Losses	118		108
Allowance for Credit Losses	6	6	6	5	6	7
Fair Value	1,854		1,965
CMBS
Debt Securities, Available-for-Sale [Line Items]
Amortized Cost	2,911		2,493
Gross Unrealized Gains	6		17
Gross Unrealized Losses	103		87
Allowance for Credit Losses	3	0	0	0	0	0
Fair Value	2,811		2,423
ABS
Debt Securities, Available-for-Sale [Line Items]
Amortized Cost	19,069		16,301
Gross Unrealized Gains	91		137
Gross Unrealized Losses	261		210
Allowance for Credit Losses	84	$ 66	50	$ 43	$ 43	$ 24
Fair Value	18,815		16,178
Hybrid and redeemable preferred securities
Debt Securities, Available-for-Sale [Line Items]
Amortized Cost	201		228
Gross Unrealized Gains	8		21
Gross Unrealized Losses	7		6
Allowance for Credit Losses	1		1
Fair Value	$ 201		$ 242