Fair Value Measurement - Fair Value Level 3 Rollforward Recurring Basis (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Variable Interest Entity, Assets [Member]
Fair Value Level 3 Rollforward
Fair value at beginning of period	$ 368	$ 560	$ 442	$ 569
Total Pretax Realized And Unrealized Gains (Losses) Recorded As Assets [Abstract]
Net Income (loss)	(50)	47	(87)	64
Other comprehensive income (loss)	0	0	0	0
Purchases	0	0	0	0
Sales	0		0
Settlements	(18)	(75)	(55)	(101)
VIE consolidations	18		18
FG VIE Deconsolidations		(6)		(6)
Transfers Into Level 3		0		0
Transfers out of Level 3			0
Fair value at end of period	318	526	318	526
Change in unrealized gains/(losses) related to financial instruments held	25	52	(11)	72
Debt Securities [Member]
Fair Value Level 3 Rollforward
Fair value at beginning of period	52		47
Total Pretax Realized And Unrealized Gains (Losses) Recorded As Assets [Abstract]
Net Income (loss)	3		8
Other comprehensive income (loss)	0		0
Purchases	5		5
Sales	0		0
Settlements	0		0
VIE consolidations	0		0
Transfers out of Level 3			0
Fair value at end of period	60		60
Change in unrealized gains/(losses) related to financial instruments held	3		8
Equity Securities and Warrants [Member]
Fair Value Level 3 Rollforward
Fair value at beginning of period	32		17
Total Pretax Realized And Unrealized Gains (Losses) Recorded As Assets [Abstract]
Net Income (loss)	7		3
Other comprehensive income (loss)	0		0
Purchases	17		50
Sales	(3)		(17)
Settlements	0		0
VIE consolidations	0		0
Transfers out of Level 3			0
Fair value at end of period	53		53
Change in unrealized gains/(losses) related to financial instruments held	7		3
Structured Products [Member]
Fair Value Level 3 Rollforward
Fair value at beginning of period	12		0
Total Pretax Realized And Unrealized Gains (Losses) Recorded As Assets [Abstract]
Net Income (loss)	3		3
Other comprehensive income (loss)	0		0
Purchases	5		17
Sales	(14)		(14)
Settlements	0		0
VIE consolidations	0		0
Transfers out of Level 3			0
Fair value at end of period	6		6
Change in unrealized gains/(losses) related to financial instruments held	1		1
Other Assets and Other Invested Assets [Member]
Fair Value Level 3 Rollforward
Fair value at beginning of period	103	68	55	77
Total Pretax Realized And Unrealized Gains (Losses) Recorded As Assets [Abstract]
Net Income (loss)	(25)	19	23	10
Other comprehensive income (loss)	0	0	0	0
Purchases	0	0	0	0
Sales	0		0
Settlements	0	0	0	0
VIE consolidations	0		0
FG VIE Deconsolidations		0		0
Transfers Into Level 3		0		0
Transfers out of Level 3			0
Fair value at end of period	78	87	78	87
Change in unrealized gains/(losses) related to financial instruments held	(25)	19	23	10
FG VIEs' liabilities with recourse, at fair value [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value at end of period	(332)	(446)	(332)	(446)
Total Pretax Realized And Unrealized Gains (Losses) Recorded As Liabilities [Abstract]
Net income (loss)	(12)	(20)	4	(31)
Other comprehensive income (loss)	(7)	5	6	5
Purchases		0		0
Issuances	0		0
Settlements	15	69	41	92
VIE consolidations	(16)		(16)
FG VIE deconsolidation		5		5
Transfers into Level 3		0		0
Fair value at start of period	(312)	(505)	(367)	(517)
Change in unrealized gains/(losses) included in earnings related to financial instruments held as of June 30, 2020	(11)	(20)	4	(31)
Change in unrealized gains/(losses) included in OCI related to financial instruments held at June 30. 2019	(7)	5	6	5
Variable Interest Liabilities without Recourse [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value at end of period	(20)	(105)	(20)	(105)
Total Pretax Realized And Unrealized Gains (Losses) Recorded As Liabilities [Abstract]
Net income (loss)	63	(3)	74	(7)
Other comprehensive income (loss)	0	0	0	0
Purchases		0		0
Issuances	0		0
Settlements	2	1	11	3
VIE consolidations	(3)		(3)
FG VIE deconsolidation		1		1
Transfers into Level 3		0		0
Fair value at start of period	(82)	(104)	(102)	(102)
Change in unrealized gains/(losses) included in earnings related to financial instruments held as of June 30, 2020	(11)	(12)	(1)	(15)
Liabilities of Consolidated Investment Vehicles [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value at end of period	(806)		(806)
Total Pretax Realized And Unrealized Gains (Losses) Recorded As Liabilities [Abstract]
Net income (loss)	(18)		37
Other comprehensive income (loss)	0		0
Issuances	(362)		(362)
Settlements	0		0
VIE consolidations	0		0
Fair value at start of period	(426)		(481)
Change in unrealized gains/(losses) included in earnings related to financial instruments held as of June 30, 2020	(18)		37
Obligations of state and political subdivisions [Member] | Fixed Maturities [Member]
Fair Value Level 3 Rollforward
Fair value at beginning of period	86	104	107	99
Total Pretax Realized And Unrealized Gains (Losses) Recorded As Assets [Abstract]
Net Income (loss)	1	1	2	2
Other comprehensive income (loss)	10	0	(11)	5
Purchases	0	0	0	0
Sales	0		0
Settlements	0	0	(1)	(1)
VIE consolidations	0		0
FG VIE Deconsolidations		0		0
Transfers Into Level 3		0		0
Transfers out of Level 3			0
Fair value at end of period	97	105	97	105
Change in unrealized gains/(losses) included in OCI related to financial instruments held at June 30. 2019	10		(11)	5
Corporate securities [Member] | Fixed Maturities [Member]
Fair Value Level 3 Rollforward
Fair value at beginning of period	26	48	41	56
Total Pretax Realized And Unrealized Gains (Losses) Recorded As Assets [Abstract]
Net Income (loss)	1	1	(6)	(10)
Other comprehensive income (loss)	2	(1)	(6)	2
Purchases	0	0	0	0
Sales	0		0
Settlements	0	0	0	0
VIE consolidations	0		0
FG VIE Deconsolidations		0		0
Transfers Into Level 3		0		0
Transfers out of Level 3			0
Fair value at end of period	29	48	29	48
Change in unrealized gains/(losses) included in OCI related to financial instruments held at June 30. 2019	2	(1)	(6)	2
RMBS [Member] | Fixed Maturities [Member]
Fair Value Level 3 Rollforward
Fair value at beginning of period	253	318	308	309
Total Pretax Realized And Unrealized Gains (Losses) Recorded As Assets [Abstract]
Net Income (loss)	2	5	5	11
Other comprehensive income (loss)	12	15	(35)	20
Purchases	0	0	0	11
Sales	0		0
Settlements	(13)	(13)	(24)	(26)
VIE consolidations	0		0
FG VIE Deconsolidations		0		0
Transfers Into Level 3		0		0
Transfers out of Level 3			0
Fair value at end of period	254	325	254	325
Change in unrealized gains/(losses) included in OCI related to financial instruments held at June 30. 2019	11	15	(34)	20
Asset-backed Securities [Member] | Fixed Maturities [Member]
Fair Value Level 3 Rollforward
Fair value at beginning of period	596	958	658	947
Total Pretax Realized And Unrealized Gains (Losses) Recorded As Assets [Abstract]
Net Income (loss)	7	30	14	44
Other comprehensive income (loss)	17	(85)	(42)	(94)
Purchases	118	8	118	18
Sales	(21)		(23)
Settlements	(3)	(238)	(10)	(242)
VIE consolidations	0		0
FG VIE Deconsolidations		0		0
Transfers Into Level 3		1		1
Transfers out of Level 3			(1)
Fair value at end of period	714	674	714	674
Change in unrealized gains/(losses) included in OCI related to financial instruments held at June 30. 2019	16	8	(41)	11
Credit Risk Contract [Member]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Fair value at start of period	(262)	(228)	(185)	(207)
Total Pretax Realized And Unrealized Gains (Losses) Recorded As Net Derivative Asset (Liability) [Abstract]
Net income (loss)	100	(8)	23	(30)
Other comprehensive income (loss)	0	0	0	0
Purchases		0		0
Settlements	1	20	1	21
Issuances	0		0
VIE consolidations	0		0
FG VIE deconsolidation		0		0
Transfers into Level 3		0		0
Fair value at end of period	(161)	(216)	(161)	(216)
Change in unrealized gains/(losses) included in earnings related to financial instruments held as of June 30, 2019	$ 100	$ (7)	$ 27	$ (28)