Investments - Investments - Unrealized Losses on AFS Securities (Details) $ in Millions	Mar. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Unrealized Loss Position, Number of Positions	3,433
Percentage of Gross Unrealized Losses Depressed Less than Twenty Percent of Cost or Amortized Cost	99.00%
ABS
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	$ 22	$ 3
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	795	396
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	4	0
Debt Securities, Available-for-sale, Unrealized Loss Position, Total	799	396
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss, Total	22	3
Collateralized Loan Obligations [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	20	2
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	2,405	1,434
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	3	0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	220	147
Debt Securities, Available-for-sale, Unrealized Loss Position, Total	2,625	1,581
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss, Total	23	2
CMBS
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	81	7
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	2,578	594
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	11	8
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	86	82
Debt Securities, Available-for-sale, Unrealized Loss Position, Total	2,664	676
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss, Total	92	15
Corporate
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	423	65
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	8,440	3,698
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	75	9
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	717	234
Debt Securities, Available-for-sale, Unrealized Loss Position, Total	9,157	3,932
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss, Total	498	74
Foreign Govt./Govt. Agencies
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	17	5
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	445	340
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	6	1
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	80	16
Debt Securities, Available-for-sale, Unrealized Loss Position, Total	525	356
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss, Total	23	6
Municipal
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	141	3
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	2,055	301
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	2	0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	24	12
Debt Securities, Available-for-sale, Unrealized Loss Position, Total	2,079	313
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss, Total	143	3
RMBS
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	138	23
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	3,064	1,869
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	21	4
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	240	94
Debt Securities, Available-for-sale, Unrealized Loss Position, Total	3,304	1,963
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss, Total	159	27
U.S. Treasuries
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	78	13
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	1,506	2,301
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	4	1
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	33	23
Debt Securities, Available-for-sale, Unrealized Loss Position, Total	1,539	2,324
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss, Total	82	14
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, Accumulated Loss	920	121
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	21,288	10,933
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	122	23
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	1,404	608
Debt Securities, Available-for-sale, Unrealized Loss Position, Total	22,692	11,541
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss, Total	$ 1,042	$ 144

Percentage of gross unrealized losses depressed less than twenty percent of cost or amortized cost.

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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for more than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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Amount of accumulated unrealized loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for 12 months or longer, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for less than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in unrealized loss position without allowance for credit loss.

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Number of investments in debt securities measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in unrealized loss position, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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