Investments - Investments - Unrealized Losses on AFS Securities (Details) $ in Millions	Sep. 30, 2023 USD ($)	Dec. 31, 2022 USD ($)
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Unrealized Loss Position, Number of Positions	5,020
Percentage of Gross Unrealized Losses Depressed Less than Twenty Percent of Cost or Amortized Cost	88.00%
ABS
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	$ 1,683	$ 1,577
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	27	50
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	1,211	281
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	59	25
Debt Securities, Available-for-sale, Unrealized Loss Position, Total	2,894	1,858
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss, Total	86	75
Collateralized Loan Obligations [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	115	1,490
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	1	48
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	2,597	1,378
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	25	54
Debt Securities, Available-for-sale, Unrealized Loss Position, Total	2,712	2,868
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss, Total	26	102
CMBS
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	192	2,560
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	12	270
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	2,845	521
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	419	88
Debt Securities, Available-for-sale, Unrealized Loss Position, Total	3,037	3,081
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss, Total	431	358
Corporate
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	4,473	11,157
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	146	1,071
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	11,098	2,575
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	1,585	521
Debt Securities, Available-for-sale, Unrealized Loss Position, Total	15,571	13,732
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss, Total	1,731	1,592
Foreign Govt./Govt. Agencies
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	110	308
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	3	26
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	413	224
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	44	23
Debt Securities, Available-for-sale, Unrealized Loss Position, Total	523	532
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss, Total	47	49
Municipal
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	1,614	4,270
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	74	461
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	3,076	228
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	571	54
Debt Securities, Available-for-sale, Unrealized Loss Position, Total	4,690	4,498
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss, Total	645	515
RMBS
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	644	2,311
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	20	249
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	3,123	1,250
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	556	259
Debt Securities, Available-for-sale, Unrealized Loss Position, Total	3,767	3,561
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss, Total	576	508
U.S. Treasuries
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	349	1,554
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	23	145
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	1,578	633
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	250	98
Debt Securities, Available-for-sale, Unrealized Loss Position, Total	1,927	2,187
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss, Total	273	243
Available-for-sale Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	9,180	25,227
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	306	2,320
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	25,941	7,090
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	3,509	1,122
Debt Securities, Available-for-sale, Unrealized Loss Position, Total	35,121	32,317
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss, Total	$ 3,815	$ 3,442