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Allowance for Expected Credit Losses (Details) - Narrative - Reinsurer Concentration Risk [Member] $ in Millions | 9 Months Ended
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Sep. 30, 2025 USD ($)
Reinsurance Recoverables [Member] | Reinsurer Group Rated by A.M. Best [Member] | A.M. Best, Rating Provided [Member] |
Reinsurance recoverables, credit quality indicator |
Reinsurance recoverables, after deducting mandatory pools and associations and before allowances for expected credit losses | $ 6,190
Concentration risk percentage | 88.00%
Reinsurance Recoverables [Member] | Reinsurer Group Not Rated by A.M. Best [Member] |
Reinsurance recoverables, credit quality indicator |
Concentration risk percentage | 12.00%
Reinsurance Recoverables [Member] | Captive Insurance Companies [Member] |
Reinsurance recoverables, credit quality indicator |
Concentration risk percentage | 6.00%
Reinsurance Recoverables [Member] | Voluntary Pools [Member] |
Reinsurance recoverables, credit quality indicator |
Concentration risk percentage | 1.00%
Reinsurance Recoverables [Member] | Other Companies [Member] |
Reinsurance recoverables, credit quality indicator |
Concentration risk percentage | 5.00%
Reinsurance Recoverables Rated by A.M. Best [Member] | Reinsurer Group Rated by A.M. Best [Member] | A.M. Best, A- Rating Or Better [Member] |
Reinsurance recoverables, credit quality indicator |
Concentration risk percentage | 95.00%

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