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Reserve for Loss and Loss Expense (Historical Claims Duration) (Details) $ in Thousands | Dec. 31, 2023 USD ($)
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Short-duration Insurance Contracts, Historical Claims Duration [Line Items] |
Net outstanding liabilities | $ 15,332,846
Standard Commercial Lines [Member] | General Liability [Member] |
Short-duration Insurance Contracts, Historical Claims Duration [Line Items] |
Short-duration Insurance Contracts, Historical Claims Duration, Year One | 6.20%
Short-duration Insurance Contracts, Historical Claims Duration, Year Two | 11.90%
Short-duration Insurance Contracts, Historical Claims Duration, Year Three | 14.40%
Short-duration Insurance Contracts, Historical Claims Duration, Year Four | 16.60%
Short-duration Insurance Contracts, Historical Claims Duration, Year Five | 14.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Six | 10.40%
Short-duration Insurance Contracts, Historical Claims Duration, Year Seven | 8.40%
Short-duration Insurance Contracts, Historical Claims Duration, Year Eight | 4.10%
Short-duration Insurance Contracts, Historical Claims Duration, Year Nine | 2.70%
Short-duration Insurance Contracts, Historical Claims Duration, Year Ten | 3.40%
Standard Commercial Lines [Member] | Workers Compensation [Member] |
Short-duration Insurance Contracts, Historical Claims Duration [Line Items] |
Short-duration Insurance Contracts, Historical Claims Duration, Year One | 22.80%
Short-duration Insurance Contracts, Historical Claims Duration, Year Two | 26.70%
Short-duration Insurance Contracts, Historical Claims Duration, Year Three | 13.20%
Short-duration Insurance Contracts, Historical Claims Duration, Year Four | 9.20%
Short-duration Insurance Contracts, Historical Claims Duration, Year Five | 4.20%
Short-duration Insurance Contracts, Historical Claims Duration, Year Six | 2.90%
Short-duration Insurance Contracts, Historical Claims Duration, Year Seven | 2.20%
Short-duration Insurance Contracts, Historical Claims Duration, Year Eight | 0.90%
Short-duration Insurance Contracts, Historical Claims Duration, Year Nine | 0.30%
Short-duration Insurance Contracts, Historical Claims Duration, Year Ten | 3.20%
Standard Commercial Lines [Member] | Commercial Automobile [Member] |
Short-duration Insurance Contracts, Historical Claims Duration [Line Items] |
Short-duration Insurance Contracts, Historical Claims Duration, Year One | 36.80%
Short-duration Insurance Contracts, Historical Claims Duration, Year Two | 17.50%
Short-duration Insurance Contracts, Historical Claims Duration, Year Three | 14.20%
Short-duration Insurance Contracts, Historical Claims Duration, Year Four | 13.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Five | 10.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Six | 3.80%
Short-duration Insurance Contracts, Historical Claims Duration, Year Seven | 2.10%
Short-duration Insurance Contracts, Historical Claims Duration, Year Eight | 0.90%
Short-duration Insurance Contracts, Historical Claims Duration, Year Nine | 0.80%
Short-duration Insurance Contracts, Historical Claims Duration, Year Ten | 0.60%
Standard Commercial Lines [Member] | Business Owners' Policies [Member] |
Short-duration Insurance Contracts, Historical Claims Duration [Line Items] |
Short-duration Insurance Contracts, Historical Claims Duration, Year One | 49.50%
Short-duration Insurance Contracts, Historical Claims Duration, Year Two | 21.40%
Short-duration Insurance Contracts, Historical Claims Duration, Year Three | 8.20%
Short-duration Insurance Contracts, Historical Claims Duration, Year Four | 8.90%
Short-duration Insurance Contracts, Historical Claims Duration, Year Five | 5.10%
Short-duration Insurance Contracts, Historical Claims Duration, Year Six | 2.80%
Short-duration Insurance Contracts, Historical Claims Duration, Year Seven | 1.50%
Short-duration Insurance Contracts, Historical Claims Duration, Year Eight | 0.70%
Short-duration Insurance Contracts, Historical Claims Duration, Year Nine | 0.40%
Short-duration Insurance Contracts, Historical Claims Duration, Year Ten | 0.20%
Standard Commercial Lines [Member] | Commercial Property [Member] |
Short-duration Insurance Contracts, Historical Claims Duration [Line Items] |
Short-duration Insurance Contracts, Historical Claims Duration, Year One | 68.80%
Short-duration Insurance Contracts, Historical Claims Duration, Year Two | 26.30%
Short-duration Insurance Contracts, Historical Claims Duration, Year Three | 3.10%
Short-duration Insurance Contracts, Historical Claims Duration, Year Four | 1.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Five | 0.50%
Short-duration Insurance Contracts, Historical Claims Duration, Year Six | 0.10%
Short-duration Insurance Contracts, Historical Claims Duration, Year Seven | 0.10%
Short-duration Insurance Contracts, Historical Claims Duration, Year Eight | 0.10%
Short-duration Insurance Contracts, Historical Claims Duration, Year Nine | 0.10%
Short-duration Insurance Contracts, Historical Claims Duration, Year Ten | 0.10%
Standard Personal Lines | Personal Automobile [Member] |
Short-duration Insurance Contracts, Historical Claims Duration [Line Items] |
Short-duration Insurance Contracts, Historical Claims Duration, Year One | 59.40%
Short-duration Insurance Contracts, Historical Claims Duration, Year Two | 19.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Three | 8.90%
Short-duration Insurance Contracts, Historical Claims Duration, Year Four | 5.90%
Short-duration Insurance Contracts, Historical Claims Duration, Year Five | 3.70%
Short-duration Insurance Contracts, Historical Claims Duration, Year Six | 1.50%
Short-duration Insurance Contracts, Historical Claims Duration, Year Seven | 0.70%
Short-duration Insurance Contracts, Historical Claims Duration, Year Eight | 0.50%
Short-duration Insurance Contracts, Historical Claims Duration, Year Nine | 0.20%
Short-duration Insurance Contracts, Historical Claims Duration, Year Ten | 0.10%
Standard Personal Lines | Homeowners [Member] |
Short-duration Insurance Contracts, Historical Claims Duration [Line Items] |
Short-duration Insurance Contracts, Historical Claims Duration, Year One | 70.70%
Short-duration Insurance Contracts, Historical Claims Duration, Year Two | 22.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Three | 3.60%
Short-duration Insurance Contracts, Historical Claims Duration, Year Four | 1.60%
Short-duration Insurance Contracts, Historical Claims Duration, Year Five | 1.20%
Short-duration Insurance Contracts, Historical Claims Duration, Year Six | 0.30%
Short-duration Insurance Contracts, Historical Claims Duration, Year Seven | 0.20%
Short-duration Insurance Contracts, Historical Claims Duration, Year Eight | 0.10%
Short-duration Insurance Contracts, Historical Claims Duration, Year Nine | 0.10%
Short-duration Insurance Contracts, Historical Claims Duration, Year Ten | 0.10%
E&S Lines [Member] | Casualty Insurance Product Line [Member] |
Short-duration Insurance Contracts, Historical Claims Duration [Line Items] |
Short-duration Insurance Contracts, Historical Claims Duration, Year One | 3.80%
Short-duration Insurance Contracts, Historical Claims Duration, Year Two | 11.60%
Short-duration Insurance Contracts, Historical Claims Duration, Year Three | 17.30%
Short-duration Insurance Contracts, Historical Claims Duration, Year Four | 20.90%
Short-duration Insurance Contracts, Historical Claims Duration, Year Five | 14.40%
Short-duration Insurance Contracts, Historical Claims Duration, Year Six | 8.40%
Short-duration Insurance Contracts, Historical Claims Duration, Year Seven | 6.80%
Short-duration Insurance Contracts, Historical Claims Duration, Year Eight | 5.90%
Short-duration Insurance Contracts, Historical Claims Duration, Year Nine | 2.20%
Short-duration Insurance Contracts, Historical Claims Duration, Year Ten | 0.90%

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