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Fair Value of Assets and Liabilities - Schedule of Assets and Liabilities Measured at Fair Value (Details) - USD ($) $ in Millions | Sep. 30, 2025 | Dec. 31, 2024
--- | --- | ---
Assets |  |
Fixed income securities, at fair value | $ 57,186 | $ 52,747
Equity securities | 5,338 | 4,463
Short-term investments | 8,743 | 4,537
Other investments | 1,017 | 824
Assets held for sale | 0 | 3,092
Total assets at fair value | 71,430 | 63,521
Counterparty and cash collateral netting | (2) | (19)
Total | 72,268 | 64,617
Liabilities |  |
Preferred stock measured at cost | 91 | 150
U.S. government and agencies |  |
Assets |  |
Fixed income securities, at fair value | 13,525 | 11,108
Municipal |  |
Assets |  |
Fixed income securities, at fair value | 6,226 | 8,842
Foreign government |  |
Assets |  |
Fixed income securities, at fair value | 1,435 | 1,364
ABS |  |
Assets |  |
Fixed income securities, at fair value | 986 | 1,145
MBS |  |
Assets |  |
Fixed income securities, at fair value | 2,134 | 96
Quoted prices in active markets for identical assets (Level 1) |  |
Assets |  |
Total assets at fair value | 21,630 | 16,956
Significant other observable inputs (Level 2) |  |
Assets |  |
Total assets at fair value | 48,936 | 45,779
Significant unobservable inputs (Level 3) |  |
Assets |  |
Total assets at fair value | 866 | 805
Reported to NAV |  |
Assets |  |
Investments reported at NAV | 838 | 1,096
Recurring basis |  |
Assets |  |
Fixed income securities, at fair value | 57,186 | 52,747
Equity securities | 5,247 | 4,313
Short-term investments | 8,743 | 4,537
Other investments | 13 | 3
Other investments | (2) | (19)
Other assets | 141 | 134
Assets held for sale |  | 1,784
Total assets at fair value | 71,330 | 63,518
Counterparty and cash collateral netting | (2) | (19)
Liabilities |  |
Other liabilities | (2) | (1)
Other liabilities | 30 | 1
Counterparty and cash collateral netting | 30 | 1
Total recurring basis liabilities | (2) | (1)
Recurring basis | U.S. government and agencies |  |
Assets |  |
Fixed income securities, at fair value | 13,525 | 11,108
Recurring basis | Municipal |  |
Assets |  |
Fixed income securities, at fair value | 6,226 | 8,842
Recurring basis | Corporate - public |  |
Assets |  |
Fixed income securities, at fair value | 21,887 | 21,233
Recurring basis | Corporate - privately placed |  |
Assets |  |
Fixed income securities, at fair value | 10,993 | 8,959
Recurring basis | Foreign government |  |
Assets |  |
Fixed income securities, at fair value | 1,435 | 1,364
Recurring basis | ABS |  |
Assets |  |
Fixed income securities, at fair value | 986 | 1,145
Recurring basis | MBS |  |
Assets |  |
Fixed income securities, at fair value | 2,134 | 96
Recurring basis | Quoted prices in active markets for identical assets (Level 1) |  |
Assets |  |
Fixed income securities, at fair value | 13,516 | 11,099
Equity securities | 4,570 | 3,600
Short-term investments | 3,543 | 2,016
Other investments | 0 | 0
Other assets | 1 | 0
Assets held for sale |  | 241
Total assets at fair value | 21,630 | 16,956
Liabilities |  |
Other liabilities | 0 | (1)
Total recurring basis liabilities | 0 | (1)
Recurring basis | Quoted prices in active markets for identical assets (Level 1) | U.S. government and agencies |  |
Assets |  |
Fixed income securities, at fair value | 13,516 | 11,099
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 | 43,364 | 41,400
Equity securities | 367 | 306
Short-term investments | 5,191 | 2,516
Other investments | 14 | 21
Other assets | 0 | 0
Assets held for sale |  | 1,536
Total assets at fair value | 48,936 | 45,779
Liabilities |  |
Other liabilities | (31) | (1)
Total recurring basis liabilities | (31) | (1)
Recurring basis | Significant other observable inputs (Level 2) | U.S. government and agencies |  |
Assets |  |
Fixed income securities, at fair value | 9 | 9
Recurring basis | Significant other observable inputs (Level 2) | Municipal |  |
Assets |  |
Fixed income securities, at fair value | 6,223 | 8,840
Recurring basis | Significant other observable inputs (Level 2) | Corporate - public |  |
Assets |  |
Fixed income securities, at fair value | 21,853 | 21,211
Recurring basis | Significant other observable inputs (Level 2) | Corporate - privately placed |  |
Assets |  |
Fixed income securities, at fair value | 10,837 | 8,849
Recurring basis | Significant other observable inputs (Level 2) | Foreign government |  |
Assets |  |
Fixed income securities, at fair value | 1,435 | 1,364
Recurring basis | Significant other observable inputs (Level 2) | ABS |  |
Assets |  |
Fixed income securities, at fair value | 962 | 1,119
Recurring basis | Significant other observable inputs (Level 2) | MBS |  |
Assets |  |
Fixed income securities, at fair value | 2,045 | 8
Recurring basis | Significant unobservable inputs (Level 3) |  |
Assets |  |
Fixed income securities, at fair value | 306 | 248
Equity securities | 310 | 407
Short-term investments | 9 | 5
Other investments | 1 | 1
Other assets | 140 | 134
Assets held for sale |  | 7
Total assets at fair value | 766 | 802
Liabilities |  |
Other liabilities | (1) | 0
Total recurring basis liabilities | (1) | 0
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 | 3 | 2
Recurring basis | Significant unobservable inputs (Level 3) | Corporate - public |  |
Assets |  |
Fixed income securities, at fair value | 34 | 22
Recurring basis | Significant unobservable inputs (Level 3) | Corporate - privately placed |  |
Assets |  |
Fixed income securities, at fair value | 156 | 110
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 | 24 | 26
Recurring basis | Significant unobservable inputs (Level 3) | MBS |  |
Assets |  |
Fixed income securities, at fair value | 89 | 88
Non-recurring basis |  |
Assets |  |
Total assets at fair value | 100 | 3
Non-recurring basis | Quoted prices in active markets for identical assets (Level 1) |  |
Assets |  |
Total assets at fair value | 0 | 0
Non-recurring basis | Significant other observable inputs (Level 2) |  |
Assets |  |
Total assets at fair value | 0 | 0
Non-recurring basis | Significant unobservable inputs (Level 3) |  |
Assets |  |
Total assets at fair value | $ 100 | $ 3

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