Investments - Investments - Unrealized Losses on AFS Securities (Details) $ in Millions	Jun. 30, 2020 USD ($)	Dec. 31, 2019 USD ($)
Debt Securities, Available-for-sale [Line Items]
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions	1,149
Percentage of Gross Unrealized Losses Depressed Less than Twenty Percent of Cost or Amortized Cost	96.00%
ABS
Debt Securities, Available-for-sale [Line Items]
Less Than 12 Months FV	$ 127	$ 398
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	1	3
12 Months or More FV	0	9
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	0
Total FV	127	407
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	1	3
CLOs
Debt Securities, Available-for-sale [Line Items]
Less Than 12 Months FV	1,435	679
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	34	2
12 Months or More FV	723	923
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	25	6
Total FV	2,158	1,602
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	59	8
CMBS
Debt Securities, Available-for-sale [Line Items]
Less Than 12 Months FV	734	538
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	59	7
12 Months or More FV	17	20
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	5	6
Total FV	751	558
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	64	13
Corporate
Debt Securities, Available-for-sale [Line Items]
Less Than 12 Months FV	1,646	789
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	99	9
12 Months or More FV	179	328
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	30	16
Total FV	1,825	1,117
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	129	25
Foreign Govt./Govt. Agencies
Debt Securities, Available-for-sale [Line Items]
Less Than 12 Months FV	136	101
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	4	0
12 Months or More FV	1	29
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	0
Total FV	137	130
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	4	0
Municipal
Debt Securities, Available-for-sale [Line Items]
Less Than 12 Months FV	319	222
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	14	2
12 Months or More FV	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	0
Total FV	319	222
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	14	2
RMBS
Debt Securities, Available-for-sale [Line Items]
Less Than 12 Months FV	195	614
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	3	3
12 Months or More FV	35	68
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	1	0
Total FV	230	682
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	4	3
U.S. Treasuries
Debt Securities, Available-for-sale [Line Items]
Less Than 12 Months FV	236	88
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	0	0
12 Months or More FV	0	34
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	1
Total FV	236	122
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	0	1
Available-for-sale Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Less Than 12 Months FV	4,828	3,429
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	214	26
12 Months or More FV	955	1,411
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	61	29
Total FV	5,783	4,840
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	$ 275	$ 55