Fair Value - Gross Components of Purchases, Sales, Issuances and Settlements, net (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Purchases	$ 1,473	$ 1,386	$ 3,468	$ 2,183
Issuances	0	0	0	0
Sales	(95)	(34)	(102)	(110)
Settlements	(111)	(116)	(656)	(437)
Purchases, (Sales), Issuances, (Settlements)	1,267	1,236	2,710	1,636
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3	462	114	254	265
Transfers (out)	(429)	(453)	(340)	(891)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers, Net	33	(339)	(86)	(626)
Purchases	0	0	0	0
Issuances	(202)	(222)	(964)	(756)
Sales	0	0	0	0
Settlements	154	119	1,075	372
Purchases, (Sales), Issuances, (Settlements), Liabilities	(48)	(103)	111	(384)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Liability, Transfers Into Level 3	0	0	0	0
Transfers (out)	0	0	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Transfers, Net	0	0	0	0
Short-term Investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Purchases	1	200	1	248
Sales	(7)	0	(7)	0
Settlements	(10)	(19)	(25)	(22)
Purchases, (Sales), Issuances, (Settlements)	(16)	181	(31)	226
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3	0	0	0	0
Transfers (out)	(88)	0	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers, Net	(88)	0	0	0
Equity securities
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Purchases	10		10
Sales	0		0
Purchases, (Sales), Issuances, (Settlements)	10	0	10	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3	0	0	0	0
Transfers (out)	0	(2)	0	(2)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers, Net	0	(2)	0	(2)
Equity securities | Related Party
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Purchases	2	31	3	243
Sales	(1)	0	(2)	(4)
Settlements	(3)	0	(4)	0
Purchases, (Sales), Issuances, (Settlements)	(2)	31	(3)	239
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3	0	0	0	0
Transfers (out)	0	0	(6)	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers, Net	0	0	(6)	0
Investment funds
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Issuances		0
Sales		(2)		(5)
Settlements		0		0
Purchases, (Sales), Issuances, (Settlements)		(2)		(5)
Investment funds | Related Party
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Purchases	16		1,525	19
Issuances	0		0	0
Sales	0		0	0
Settlements	0		0	0
Purchases, (Sales), Issuances, (Settlements)	16		1,525	19
U.S. state, municipal and political subdivisions | AFS securities
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Purchases	0		0	40
Sales	(5)		(5)	0
Settlements	0		(1)	0
Purchases, (Sales), Issuances, (Settlements)	(5)	0	(6)	40
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3	0		0	0
Transfers (out)	0		0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers, Net	0	0	0	0
Foreign governments | AFS securities
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Purchases	1		1
Sales	0		0
Settlements	0		0
Purchases, (Sales), Issuances, (Settlements)	1		1
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3	0		0
Transfers (out)	0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers, Net	0		0
Corporate | AFS securities
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Purchases	58	199	245	277
Sales	0	0	0	(2)
Settlements	(19)	(10)	(127)	(111)
Purchases, (Sales), Issuances, (Settlements)	39	189	118	164
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3	157	1	97	1
Transfers (out)	(206)	(71)	(40)	(134)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers, Net	(49)	(70)	57	(133)
Corporate | AFS securities | Related Party
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Purchases	761		761
Sales	0		0
Settlements	0		0
Purchases, (Sales), Issuances, (Settlements)	761		761
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3	0		0
Transfers (out)	0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers, Net	0		0
Corporate | Trading securities
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Purchases		0	0
Sales		0	0
Settlements		0	0
Purchases, (Sales), Issuances, (Settlements)	0	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3		0	6
Transfers (out)		(6)	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers, Net	0	(6)	6
CLO | AFS securities
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Purchases	12	37	90	64
Sales	(18)	0	(25)	0
Settlements	(1)	(3)	(9)	(4)
Purchases, (Sales), Issuances, (Settlements)	(7)	34	56	60
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3	36	0	36	0
Transfers (out)	0	(104)	(22)	(39)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers, Net	36	(104)	14	(39)
CLO | AFS securities | Related Party
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Purchases	11	0	11
Sales	0		0
Settlements	0		0
Purchases, (Sales), Issuances, (Settlements)	11	0	11
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3	0	0	0
Transfers (out)	0	(37)	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers, Net	0	(37)	0
CLO | Trading securities
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Purchases				0
Sales				0
Settlements				0
Purchases, (Sales), Issuances, (Settlements)	0	0	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3				6
Transfers (out)				0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers, Net	0	0	0	6
CLO | Trading securities | Related Party
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Purchases	0	0	13	0
Sales	0	(7)	(12)	(54)
Settlements	0	0	0	0
Purchases, (Sales), Issuances, (Settlements)	0	(7)	1	(54)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3	4	0	0	43
Transfers (out)	(24)	(23)	0	(35)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers, Net	(20)	(23)	0	8
RMBS | AFS securities
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Purchases	0			2
Sales	(1)			0
Settlements	(1)			0
Purchases, (Sales), Issuances, (Settlements)	(2)			2
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3	0			0
Transfers (out)	(16)			(62)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers, Net	(16)			(62)
RMBS | Trading securities
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Purchases	0	15	0	15
Sales	0	0	0	0
Settlements	0	0	0	0
Purchases, (Sales), Issuances, (Settlements)	0	15	0	15
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3	8	35	12	34
Transfers (out)	(1)	0	(1)	(79)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers, Net	7	35	11	(45)
ABS | AFS securities
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Purchases	47	64	95	260
Sales	(43)	(21)	(6)	(41)
Settlements	(48)	(27)	(390)	(176)
Purchases, (Sales), Issuances, (Settlements)	(44)	16	(301)	43
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3	218	0	64	0
Transfers (out)	(71)	(137)	(106)	(419)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers, Net	147	(137)	(42)	(419)
ABS | AFS securities | Related Party
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Purchases	2	587	7	757
Sales	(10)	0	(15)	0
Settlements	(23)	0	(77)	(9)
Purchases, (Sales), Issuances, (Settlements)	(31)	587	(85)	748
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3	0	0	0	0
Transfers (out)	0	0	(165)	(103)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers, Net	0	0	(165)	(103)
ABS | Trading securities
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Purchases	35	0	35	6
Sales	0	0	(16)	0
Settlements	0	(1)	0	(1)
Purchases, (Sales), Issuances, (Settlements)	35	(1)	19	5
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3	0	78	0	78
Transfers (out)	0	0	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers, Net	0	78	0	78
ABS | Trading securities | Related Party
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Purchases	517	2	671	0
Sales	(10)	0	(10)	0
Settlements	0	0	(14)	(15)
Purchases, (Sales), Issuances, (Settlements)	507	2	647	(15)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3	0	0	0
Transfers (out)	0	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers, Net	0	0	0	103
CMBS | AFS securities
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Purchases	0	251	0	252
Sales	0	(4)	(4)	(4)
Settlements	0	(52)	(1)	(94)
Purchases, (Sales), Issuances, (Settlements)	0	195	(5)	154
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3	39	0	39	0
Transfers (out)	(23)	(73)	0	(18)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers, Net	16	(73)	39	(18)
Mortgage loans
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Settlements	(6)	(4)	(8)	(5)
Purchases, (Sales), Issuances, (Settlements)	(6)	(4)	(8)	(5)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3	0	0	0	0
Transfers (out)	0	0	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers, Net	0	0	0	0
Short-term Investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Purchases, (Sales), Issuances, (Settlements)	(16)	181	(31)	226
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers, Net	(88)	0	0	0
Investment funds
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Purchases, (Sales), Issuances, (Settlements)	0	(2)	0	(5)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3		0		0
Transfers (out)		0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers, Net	0	0	0	0
Investment funds | Related Party
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Purchases, (Sales), Issuances, (Settlements)	16	0	1,525	19
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3	0		0	0
Transfers (out)	0		0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers, Net	0	0	0	0
Reinsurance Recoverable Including Reinsurance Premium Paid [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Purchases, (Sales), Issuances, (Settlements)	0	0	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers, Net	0	0	0	0
Embedded derivatives | Funds withheld at interest
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Purchases, (Sales), Issuances, (Settlements)	0	0	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers, Net	0	0	0	0
Embedded derivatives | Funds withheld at interest | Related Party
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Purchases, (Sales), Issuances, (Settlements)	0	0	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers, Net	0	0	0	0
Consolidated Entity Excluding Variable Interest Entities (VIE) | ABS | Trading securities | Related Party
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3				103
Transfers (out)				0
Interest sensitive contract liabilities | Embedded derivatives
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Purchases	0	0	0	0
Issuances	(202)	(222)	(964)	(756)
Sales	0	0	0	0
Settlements	154	119	1,075	372
Purchases, (Sales), Issuances, (Settlements), Liabilities	(48)	(103)	111	(384)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Liability, Transfers Into Level 3	0	0	0	0
Transfers (out)	0	0	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Transfers, Net	0	0	0	0
Derivative Financial Instruments, Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Purchases, (Sales), Issuances, (Settlements), Liabilities	0	0	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Transfers, Net	$ 0	$ 0	$ 0	$ 0