Investments - Unrealized Losses on AFS Securities (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
ABS
Debt Securities, Available-for-sale [Line Items]
Less Than 12 Months Amortized Cost	$ 401	$ 566
Less Than 12 Months FV	398	566
Less Than 12 Months UL	(3)	0
12 Months or More Amortized Cost	9	113
12 Months or More FV	9	112
12 Months or More UL	0	(1)
Total Amortized Cost	410	679
Total FV	407	678
Total UL	(3)	(1)
Collateralized loan obligations (CLOs)
Debt Securities, Available-for-sale [Line Items]
Less Than 12 Months Amortized Cost	681	1,358
Less Than 12 Months FV	679	1,338
Less Than 12 Months UL	(2)	(20)
12 Months or More Amortized Cost	929	7
12 Months or More FV	923	7
12 Months or More UL	(6)	0
Total Amortized Cost	1,610	1,365
Total FV	1,602	1,345
Total UL	(8)	(20)
CMBS
Debt Securities, Available-for-sale [Line Items]
Less Than 12 Months Amortized Cost	545	896
Less Than 12 Months FV	538	882
Less Than 12 Months UL	(7)	(14)
12 Months or More Amortized Cost	26	1,129
12 Months or More FV	20	1,079
12 Months or More UL	(6)	(50)
Total Amortized Cost	571	2,025
Total FV	558	1,961
Total UL	(13)	(64)
Corporate
Debt Securities, Available-for-sale [Line Items]
Less Than 12 Months Amortized Cost	798	7,174
Less Than 12 Months FV	789	6,903
Less Than 12 Months UL	(9)	(271)
12 Months or More Amortized Cost	344	2,541
12 Months or More FV	328	2,366
12 Months or More UL	(16)	(175)
Total Amortized Cost	1,142	9,715
Total FV	1,117	9,269
Total UL	(25)	(446)
Foreign government/government agencies
Debt Securities, Available-for-sale [Line Items]
Less Than 12 Months Amortized Cost	101	407
Less Than 12 Months FV	101	391
Less Than 12 Months UL	0	(16)
12 Months or More Amortized Cost	29	203
12 Months or More FV	29	193
12 Months or More UL	0	(10)
Total Amortized Cost	130	610
Total FV	130	584
Total UL	0	(26)
Municipal
Debt Securities, Available-for-sale [Line Items]
Less Than 12 Months Amortized Cost	224	1,643
Less Than 12 Months FV	222	1,613
Less Than 12 Months UL	(2)	(30)
12 Months or More Amortized Cost	0	292
12 Months or More FV	0	275
12 Months or More UL	0	(17)
Total Amortized Cost	224	1,935
Total FV	222	1,888
Total UL	(2)	(47)
Residential mortgage-backed securities (RMBS)
Debt Securities, Available-for-sale [Line Items]
Less Than 12 Months Amortized Cost	617	1,344
Less Than 12 Months FV	614	1,329
Less Than 12 Months UL	(3)	(15)
12 Months or More Amortized Cost	68	648
12 Months or More FV	68	628
12 Months or More UL	0	(20)
Total Amortized Cost	685	1,992
Total FV	682	1,957
Total UL	(3)	(35)
U.S. Treasuries
Debt Securities, Available-for-sale [Line Items]
Less Than 12 Months Amortized Cost	88	497
Less Than 12 Months FV	88	492
Less Than 12 Months UL	0	(5)
12 Months or More Amortized Cost	35	339
12 Months or More FV	34	329
12 Months or More UL	(1)	(10)
Total Amortized Cost	123	836
Total FV	122	821
Total UL	(1)	(15)
Securities available-for-sale and other
Debt Securities, Available-for-sale [Line Items]
Less Than 12 Months Amortized Cost	3,455	13,885
Less Than 12 Months FV	3,429	13,514
Less Than 12 Months UL	(26)	(371)
12 Months or More Amortized Cost	1,440	5,272
12 Months or More FV	1,411	4,989
12 Months or More UL	(29)	(283)
Total Amortized Cost	4,895	19,157
Total FV	4,840	18,503
Total UL	$ (55)	$ (654)