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Schedule IV - Reinsurance (Details) - USD ($) $ in Millions | 12 Months Ended
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Dec. 31, 2024 | Dec. 31, 2023 | Dec. 31, 2022
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items] |  |  |  |
Gross Amount |  | $ 10,056 | $ 9,652 | $ 8,542
Ceded to other Companies |  | (5,779) | (4,935) | (4,249)
Assumed From Other Companies |  | 11,455 | 8,751 | 6,785
Net Amount |  | $ 15,732 | $ 13,468 | $ 11,078
Percentage of Amount Assumed to Net |  | 72.80% | 65.00% | 61.20%
Operating segments | Insurance |  |  |  |
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items] |  |  |  |
Gross Amount |  | $ 7,970 | $ 7,865 | $ 6,889
Ceded to other Companies | [1],[2] | (2,179) | (2,049) | (1,910)
Assumed From Other Companies | [1] | 1,083 | 46 | 42
Net Amount |  | $ 6,874 | $ 5,862 | $ 5,021
Percentage of Amount Assumed to Net |  | 15.80% | 0.80% | 0.80%
Operating segments | Reinsurance |  |  |  |
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items] |  |  |  |
Gross Amount |  | $ 956 | $ 626 | $ 397
Ceded to other Companies | [1],[2] | (3,366) | (2,559) | (2,024)
Assumed From Other Companies | [1] | 10,156 | 8,487 | 6,553
Net Amount |  | $ 7,746 | $ 6,554 | $ 4,924
Percentage of Amount Assumed to Net |  | 131.10% | 129.50% | 133.10%
Operating segments | Mortgage |  |  |  |
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items] |  |  |  |
Gross Amount |  | $ 1,130 | $ 1,161 | $ 1,256
Ceded to other Companies | [1],[2] | (239) | (335) | (322)
Assumed From Other Companies | [1] | 221 | 226 | 199
Net Amount |  | $ 1,112 | $ 1,052 | $ 1,133
Percentage of Amount Assumed to Net |  | 19.90% | 21.50% | 17.60%
[1] | Certain amounts included in the gross premiums written of each segment are related to intersegment transactions and are included in the gross premiums written of each segment. Accordingly, the sum of gross premiums written for each segment does not agree to the total gross premiums written as shown in the table above due to the elimination of intersegment transactions in the total.
[2] | Certain assumed and ceded amounts related to intersegment transactions are included in individual segment results. Accordingly, the sum of such transactions for each segment does not agree to the total due to eliminations.

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