Investments - Unrealized Losses on AFS Securities (Details) $ in Millions	Mar. 31, 2021 USD ($) security	Dec. 31, 2020 USD ($)
Debt Securities, Available-for-sale [Line Items]
Fair Value, Less than 12 months	$ 23,822	$ 7,684
Fair Value, 12 months or greater	4,401	3,834
Total	28,223	11,518
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	901	254
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	202	234
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	1,103	488
Investments, excluding investments in Related Party
Debt Securities, Available-for-sale [Line Items]
Fair Value, Less than 12 months	20,959	6,336
Fair Value, 12 months or greater	4,171	3,602
Total	25,130	9,938
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	860	221
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	198	224
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	$ 1,058	445
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Number of Positions \| security	480
Debt Securities, Available-for-sale, Unrealized Loss Position, Number of Positions \| security	3,556
Related Party
Debt Securities, Available-for-sale [Line Items]
Fair Value, Less than 12 months	$ 2,863	1,348
Fair Value, 12 months or greater	230	232
Total	3,093	1,580
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	41	33
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	4	10
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	$ 45	43
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Number of Positions \| security	8
Debt Securities, Available-for-sale, Unrealized Loss Position, Number of Positions \| security	56
U.S. government and agencies \| Investments, excluding investments in Related Party
Debt Securities, Available-for-sale [Line Items]
Fair Value, Less than 12 months	$ 312	31
Fair Value, 12 months or greater	0	0
Total	312	31
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	25	1
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	0
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	25	1
U.S. state, municipal and political subdivisions \| Investments, excluding investments in Related Party
Debt Securities, Available-for-sale [Line Items]
Fair Value, Less than 12 months	226	9
Fair Value, 12 months or greater	6	6
Total	232	15
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	7	0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	0
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	7	0
Foreign governments \| Investments, excluding investments in Related Party
Debt Securities, Available-for-sale [Line Items]
Fair Value, Less than 12 months	211	2
Fair Value, 12 months or greater	1	0
Total	212	2
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	9	0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	0
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	9	0
Corporate \| Investments, excluding investments in Related Party
Debt Securities, Available-for-sale [Line Items]
Fair Value, Less than 12 months	15,665	2,218
Fair Value, 12 months or greater	398	248
Total	16,063	2,466
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	749	66
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	43	24
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	792	90
CLO \| Investments, excluding investments in Related Party
Debt Securities, Available-for-sale [Line Items]
Fair Value, Less than 12 months	2,643	1,649
Fair Value, 12 months or greater	2,873	3,179
Total	5,516	4,828
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	19	33
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	89	167
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	108	200
CLO \| Related Party
Debt Securities, Available-for-sale [Line Items]
Fair Value, Less than 12 months	601	336
Fair Value, 12 months or greater	216	232
Total	817	568
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	1	3
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	4	10
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	5	13
ABS \| Investments, excluding investments in Related Party
Debt Securities, Available-for-sale [Line Items]
Fair Value, Less than 12 months	752	1,169
Fair Value, 12 months or greater	524	84
Total	1,276	1,253
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	21	73
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	40	18
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	61	91
ABS \| Related Party
Debt Securities, Available-for-sale [Line Items]
Fair Value, Less than 12 months	2,262	1,012
Fair Value, 12 months or greater	14	0
Total	2,276	1,012
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	40	30
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	0
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	40	30
CMBS \| Investments, excluding investments in Related Party
Debt Securities, Available-for-sale [Line Items]
Fair Value, Less than 12 months	588	710
Fair Value, 12 months or greater	245	48
Total	833	758
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	23	37
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	22	13
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	45	50
RMBS \| Investments, excluding investments in Related Party
Debt Securities, Available-for-sale [Line Items]
Fair Value, Less than 12 months	562	548
Fair Value, 12 months or greater	124	37
Total	686	585
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	7	11
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	4	2
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	$ 11	$ 13

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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