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Fair Value of Assets and Liabilities - Assets and liabilities measured at fair value on a recurring and non-recurring basis (Details) - USD ($) $ in Millions | Jun. 30, 2021 | Dec. 31, 2020
--- | --- | ---
Assets |  |
Fixed income securities, at fair value | $ 42,825 | $ 42,565
Equity securities, at fair value | 3,059 | 3,168
Short-term investments, at fair value | 5,516 | 6,807
Other investments | 3,311 | 1,691
Assets held for sale | 36,969 | 42,131
Total assets at fair value | 83,523 | 82,413
Counterparty and cash collateral netting | $ (19) | $ (15)
Assets as a percent of assets measured at fair value | 0.00% | 0.00%
Total | $ 85,524 | $ 84,237
Liabilities |  |
Liabilities held for sale | $ (32,775) | $ (33,325)
Liabilities as a percent of liabilities measured at fair value | (2.60%) | (4.20%)
Fair value |  |
Assets |  |
Assets as a percent of assets measured at fair value | 100.00% | 100.00%
Liabilities |  |
Liabilities as a percent of liabilities measured at fair value | 100.00% | 100.00%
U.S. government and agencies |  |
Assets |  |
Fixed income securities, at fair value | $ 4,775 | $ 2,107
Municipal |  |
Assets |  |
Fixed income securities, at fair value | 7,649 | 7,578
Foreign government |  |
Assets |  |
Fixed income securities, at fair value | 1,006 | 958
ABS |  |
Assets |  |
Fixed income securities, at fair value | 1,066 | 846
MBS |  |
Assets |  |
Fixed income securities, at fair value | 51 | 59
Quoted prices in active markets for identical assets (Level 1) |  |
Assets |  |
Total assets at fair value | $ 16,486 | $ 17,567
Assets as a percent of assets measured at fair value | 19.70% | 21.30%
Liabilities |  |
Liabilities as a percent of liabilities measured at fair value | 0.00% | 0.00%
Significant other observable inputs (Level 2) |  |
Assets |  |
Total assets at fair value | $ 66,287 | $ 64,029
Assets as a percent of assets measured at fair value | 79.40% | 77.70%
Liabilities |  |
Liabilities as a percent of liabilities measured at fair value | 24.20% | 23.80%
Significant unobservable inputs (Level 3) |  |
Assets |  |
Total assets at fair value | $ 769 | $ 832
Assets as a percent of assets measured at fair value | 0.90% | 1.00%
Liabilities |  |
Liabilities as a percent of liabilities measured at fair value | 78.40% | 80.40%
Significant unobservable inputs (Level 3) | Fair value |  |
Assets |  |
Assets held for sale | $ 3,239 | $ 4,440
Liabilities |  |
Liabilities held for sale | (8,489) | (9,424)
Fair Value Net Asset Value |  |
Assets |  |
Assets held for sale | 518 | 762
Investments reported at NAV | 1,483 | 1,062
Recurring basis |  |
Assets |  |
Fixed income securities, at fair value | 42,825 | 42,565
Equity securities, at fair value | 3,059 | 3,168
Short-term investments, at fair value | 5,516 | 6,807
Other investments | 50 | 20
Other investments | (14) | (9)
Other assets |  | 1
Assets held for sale | 32,031 | 29,852
Assets held for sale | (5) | (6)
Total assets at fair value | 83,481 | 82,413
Counterparty and cash collateral netting | (19) | (15)
Liabilities |  |
Other liabilities | (23) | (16)
Other liabilities | 13 | 18
Liabilities held for sale | (602) | (626)
Liabilities held for sale counterparty and cash collateral netting | 3 | 9
Total recurring basis liabilities | (625) | (642)
Counterparty and cash collateral netting | 16 | 27
Recurring basis | U.S. government and agencies |  |
Assets |  |
Fixed income securities, at fair value | 4,775 | 2,106
Recurring basis | Municipal |  |
Assets |  |
Fixed income securities, at fair value | 7,649 | 7,579
Recurring basis | Corporate - public |  |
Assets |  |
Fixed income securities, at fair value | 18,517 | 21,952
Recurring basis | Corporate - privately placed |  |
Assets |  |
Fixed income securities, at fair value | 9,761 | 9,065
Recurring basis | Foreign government |  |
Assets |  |
Fixed income securities, at fair value | 1,006 | 958
Recurring basis | ABS |  |
Assets |  |
Fixed income securities, at fair value | 1,066 | 846
Recurring basis | MBS |  |
Assets |  |
Fixed income securities, at fair value | 51 | 59
Recurring basis | Quoted prices in active markets for identical assets (Level 1) |  |
Assets |  |
Fixed income securities, at fair value | 4,739 | 2,061
Equity securities, at fair value | 2,248 | 2,468
Short-term investments, at fair value | 3,515 | 6,549
Other investments | 0 | 0
Other assets |  | 1
Assets held for sale | 5,984 | 6,488
Total assets at fair value | 16,486 | 17,567
Liabilities |  |
Other liabilities | 0 | 0
Liabilities held for sale | 0 | 0
Total recurring basis liabilities | 0 | 0
Recurring basis | Quoted prices in active markets for identical assets (Level 1) | U.S. government and agencies |  |
Assets |  |
Fixed income securities, at fair value | 4,739 | 2,061
Recurring basis | Quoted prices in active markets for identical assets (Level 1) | Municipal |  |
Assets |  |
Fixed income securities, at fair value | 0 | 0
Recurring basis | Quoted prices in active markets for identical assets (Level 1) | Corporate - public |  |
Assets |  |
Fixed income securities, at fair value | 0 | 0
Recurring basis | Quoted prices in active markets for identical assets (Level 1) | Corporate - privately placed |  |
Assets |  |
Fixed income securities, at fair value | 0 | 0
Recurring basis | Quoted prices in active markets for identical assets (Level 1) | Foreign government |  |
Assets |  |
Fixed income securities, at fair value | 0 | 0
Recurring basis | Quoted prices in active markets for identical assets (Level 1) | ABS |  |
Assets |  |
Fixed income securities, at fair value | 0 | 0
Recurring basis | Quoted prices in active markets for identical assets (Level 1) | MBS |  |
Assets |  |
Fixed income securities, at fair value | 0 | 0
Recurring basis | Significant other observable inputs (Level 2) |  |
Assets |  |
Fixed income securities, at fair value | 37,931 | 40,278
Equity securities, at fair value | 406 | 396
Short-term investments, at fair value | 2,001 | 223
Other investments | 61 | 29
Other assets |  | 0
Assets held for sale | 25,888 | 23,103
Total assets at fair value | 66,287 | 64,029
Liabilities |  |
Other liabilities | (36) | (34)
Liabilities held for sale | (115) | (119)
Total recurring basis liabilities | (151) | (153)
Recurring basis | Significant other observable inputs (Level 2) | U.S. government and agencies |  |
Assets |  |
Fixed income securities, at fair value | 36 | 45
Recurring basis | Significant other observable inputs (Level 2) | Municipal |  |
Assets |  |
Fixed income securities, at fair value | 7,631 | 7,562
Recurring basis | Significant other observable inputs (Level 2) | Corporate - public |  |
Assets |  |
Fixed income securities, at fair value | 18,497 | 21,885
Recurring basis | Significant other observable inputs (Level 2) | Corporate - privately placed |  |
Assets |  |
Fixed income securities, at fair value | 9,677 | 9,002
Recurring basis | Significant other observable inputs (Level 2) | Foreign government |  |
Assets |  |
Fixed income securities, at fair value | 1,006 | 958
Recurring basis | Significant other observable inputs (Level 2) | ABS |  |
Assets |  |
Fixed income securities, at fair value | 1,056 | 794
Recurring basis | Significant other observable inputs (Level 2) | MBS |  |
Assets |  |
Fixed income securities, at fair value | 28 | 32
Recurring basis | Significant unobservable inputs (Level 3) |  |
Assets |  |
Fixed income securities, at fair value | 155 | 226
Equity securities, at fair value | 405 | 304
Short-term investments, at fair value | 0 | 35
Other investments | 3 | 0
Other assets |  | 0
Assets held for sale | 164 | 267
Total assets at fair value | 727 | 832
Liabilities |  |
Other liabilities | 0 | 0
Liabilities held for sale | (490) | (516)
Total recurring basis liabilities | (490) | (516)
Recurring basis | Significant unobservable inputs (Level 3) | U.S. government and agencies |  |
Assets |  |
Fixed income securities, at fair value | 0 | 0
Recurring basis | Significant unobservable inputs (Level 3) | Municipal |  |
Assets |  |
Fixed income securities, at fair value | 18 | 17
Recurring basis | Significant unobservable inputs (Level 3) | Corporate - public |  |
Assets |  |
Fixed income securities, at fair value | 20 | 67
Recurring basis | Significant unobservable inputs (Level 3) | Corporate - privately placed |  |
Assets |  |
Fixed income securities, at fair value | 84 | 63
Recurring basis | Significant unobservable inputs (Level 3) | Foreign government |  |
Assets |  |
Fixed income securities, at fair value | 0 | 0
Recurring basis | Significant unobservable inputs (Level 3) | ABS |  |
Assets |  |
Fixed income securities, at fair value | 10 | 52
Recurring basis | Significant unobservable inputs (Level 3) | MBS |  |
Assets |  |
Fixed income securities, at fair value | 23 | $ 27
Non-recurring basis |  |
Assets |  |
Total assets at fair value | 42 |
Non-recurring basis | Quoted prices in active markets for identical assets (Level 1) |  |
Assets |  |
Total assets at fair value | 0 |
Non-recurring basis | Significant other observable inputs (Level 2) |  |
Assets |  |
Total assets at fair value | 0 |
Non-recurring basis | Significant unobservable inputs (Level 3) |  |
Assets |  |
Total assets at fair value | $ 42 |

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