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Investments - Schedule of Amortized Cost, Allowance for Credit Losses, Gross Unrealized Gains and Losses and Fair Value of AFS Investments by Asset Type (Details) - USD ($) $ in Millions	Sep. 30, 2025	Jun. 30, 2025	Dec. 31, 2024	Sep. 30, 2024	Jun. 30, 2024	Dec. 31, 2023
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 227,740		$ 199,895
Allowance for Credit Losses	(783)	$ (761)	(709)	$ (678)	$ (671)	$ (591)
Gross Unrealized Gains	3,936		1,257
Gross Unrealized Losses	(12,209)		(16,276)
Fair Value	218,684		184,167
Nonrelated Party
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	203,087		180,716
Allowance for Credit Losses	(782)	(760)	(708)	(677)	(670)	(590)
Gross Unrealized Gains	3,714		1,200
Gross Unrealized Losses	(11,998)		(15,844)
Fair Value	194,021		165,364
Related Party
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	24,653		19,179
Allowance for Credit Losses	(1)		(1)
Gross Unrealized Gains	222		57
Gross Unrealized Losses	(211)		(432)
Fair Value	24,663		18,803
U.S. government and agencies \| Nonrelated Party
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	14,459		8,413
Allowance for Credit Losses	0		0
Gross Unrealized Gains	141		8
Gross Unrealized Losses	(1,100)		(1,270)
Fair Value	13,500		7,151
U.S. state, municipal and political subdivisions \| Nonrelated Party
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	1,043		1,167
Allowance for Credit Losses	0		0
Gross Unrealized Gains	0		0
Gross Unrealized Losses	(211)		(246)
Fair Value	832		921
Foreign governments \| Nonrelated Party
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	2,244		2,082
Allowance for Credit Losses	0		0
Gross Unrealized Gains	40		0
Gross Unrealized Losses	(544)		(514)
Fair Value	1,740		1,568
Corporate \| Nonrelated Party
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	101,132		95,006
Allowance for Credit Losses	(151)	(174)	(175)	(168)	(168)	(129)
Gross Unrealized Gains	1,530		485
Gross Unrealized Losses	(9,001)		(11,731)
Fair Value	93,510		83,585
Corporate \| Related Party
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	2,291		2,150
Allowance for Credit Losses	0		0
Gross Unrealized Gains	27		18
Gross Unrealized Losses	(18)		(31)
Fair Value	2,300		2,137
CLO \| Nonrelated Party
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	29,252		29,524
Allowance for Credit Losses	0		0	(1)	0	(2)
Gross Unrealized Gains	781		266
Gross Unrealized Losses	(81)		(608)
Fair Value	29,952		29,182
CLO \| Related Party
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	7,227		6,130
Allowance for Credit Losses	0		0
Gross Unrealized Gains	147		18
Gross Unrealized Losses	(8)		(113)
Fair Value	7,366		6,035
ABS \| Nonrelated Party
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	30,437		24,779
Allowance for Credit Losses	(160)	(130)	(76)	(74)	(67)	(49)
Gross Unrealized Gains	745		138
Gross Unrealized Losses	(422)		(640)
Fair Value	30,600		24,201
ABS \| Related Party
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	14,973		10,899
Allowance for Credit Losses	(1)	(1)	(1)	(1)	(1)	(1)
Gross Unrealized Gains	48		21
Gross Unrealized Losses	(184)		(288)
Fair Value	14,836		10,631
CMBS \| Nonrelated Party
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	13,607		11,158
Allowance for Credit Losses	(67)	(62)	(60)	(57)	(57)	(29)
Gross Unrealized Gains	126		75
Gross Unrealized Losses	(347)		(432)
Fair Value	13,319		10,741
CMBS \| Related Party
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	162
Allowance for Credit Losses	0
Gross Unrealized Gains	0
Gross Unrealized Losses	(1)
Fair Value	161
RMBS \| Nonrelated Party
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	10,913		8,587
Allowance for Credit Losses	(404)	$ (394)	(397)	$ (377)	$ (378)	$ (381)
Gross Unrealized Gains	351		228
Gross Unrealized Losses	(292)		(403)
Fair Value	$ 10,568		$ 8,015