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Reserve for Loss and Loss Expense (Historical Claims Duration) (Details) $ in Thousands | Dec. 31, 2021 USD ($)
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Short-duration Insurance Contracts, Historical Claims Duration [Line Items] |
Net outstanding liabilities | $ 12,898,946
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 | 6.40%
Short-duration Insurance Contracts, Historical Claims Duration, Year Two | 11.90%
Short-duration Insurance Contracts, Historical Claims Duration, Year Three | 15.60%
Short-duration Insurance Contracts, Historical Claims Duration, Year Four | 17.60%
Short-duration Insurance Contracts, Historical Claims Duration, Year Five | 14.40%
Short-duration Insurance Contracts, Historical Claims Duration, Year Six | 9.80%
Short-duration Insurance Contracts, Historical Claims Duration, Year Seven | 6.60%
Short-duration Insurance Contracts, Historical Claims Duration, Year Eight | 5.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Nine | 1.90%
Short-duration Insurance Contracts, Historical Claims Duration, Year Ten | 1.60%
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 | 21.80%
Short-duration Insurance Contracts, Historical Claims Duration, Year Two | 25.90%
Short-duration Insurance Contracts, Historical Claims Duration, Year Three | 13.60%
Short-duration Insurance Contracts, Historical Claims Duration, Year Four | 8.40%
Short-duration Insurance Contracts, Historical Claims Duration, Year Five | 4.50%
Short-duration Insurance Contracts, Historical Claims Duration, Year Six | 2.90%
Short-duration Insurance Contracts, Historical Claims Duration, Year Seven | 2.30%
Short-duration Insurance Contracts, Historical Claims Duration, Year Eight | 3.10%
Short-duration Insurance Contracts, Historical Claims Duration, Year Nine | 1.70%
Short-duration Insurance Contracts, Historical Claims Duration, Year Ten | 0.80%
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 | 37.20%
Short-duration Insurance Contracts, Historical Claims Duration, Year Two | 16.70%
Short-duration Insurance Contracts, Historical Claims Duration, Year Three | 14.70%
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 | 4.50%
Short-duration Insurance Contracts, Historical Claims Duration, Year Seven | 1.70%
Short-duration Insurance Contracts, Historical Claims Duration, Year Eight | 1.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Nine | 0.50%
Short-duration Insurance Contracts, Historical Claims Duration, Year Ten | 0.10%
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 | 49.20%
Short-duration Insurance Contracts, Historical Claims Duration, Year Two | 20.80%
Short-duration Insurance Contracts, Historical Claims Duration, Year Three | 8.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Four | 8.70%
Short-duration Insurance Contracts, Historical Claims Duration, Year Five | 5.90%
Short-duration Insurance Contracts, Historical Claims Duration, Year Six | 3.10%
Short-duration Insurance Contracts, Historical Claims Duration, Year Seven | 1.20%
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%
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 | 69.40%
Short-duration Insurance Contracts, Historical Claims Duration, Year Two | 25.80%
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 | 0.40%
Short-duration Insurance Contracts, Historical Claims Duration, Year Six | 0.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Seven | 0.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Eight | 0.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Nine | 0.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Ten | 0.00%
Standard Personal Lines | Personal Automobile [Member] |
Short-duration Insurance Contracts, Historical Claims Duration [Line Items] |
Short-duration Insurance Contracts, Historical Claims Duration, Year One | 59.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Two | 18.10%
Short-duration Insurance Contracts, Historical Claims Duration, Year Three | 10.30%
Short-duration Insurance Contracts, Historical Claims Duration, Year Four | 6.40%
Short-duration Insurance Contracts, Historical Claims Duration, Year Five | 3.70%
Short-duration Insurance Contracts, Historical Claims Duration, Year Six | 1.40%
Short-duration Insurance Contracts, Historical Claims Duration, Year Seven | 0.30%
Short-duration Insurance Contracts, Historical Claims Duration, Year Eight | 0.40%
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 | Homeowners [Member] |
Short-duration Insurance Contracts, Historical Claims Duration [Line Items] |
Short-duration Insurance Contracts, Historical Claims Duration, Year One | 71.50%
Short-duration Insurance Contracts, Historical Claims Duration, Year Two | 21.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Three | 3.40%
Short-duration Insurance Contracts, Historical Claims Duration, Year Four | 1.80%
Short-duration Insurance Contracts, Historical Claims Duration, Year Five | 1.60%
Short-duration Insurance Contracts, Historical Claims Duration, Year Six | 0.10%
Short-duration Insurance Contracts, Historical Claims Duration, Year Seven | 0.20%
Short-duration Insurance Contracts, Historical Claims Duration, Year Eight | 0.20%
Short-duration Insurance Contracts, Historical Claims Duration, Year Nine | 0.20%
Short-duration Insurance Contracts, Historical Claims Duration, Year Ten | 0.00%
E&S Lines [Member] | General Liability [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 | 11.20%
Short-duration Insurance Contracts, Historical Claims Duration, Year Three | 16.70%
Short-duration Insurance Contracts, Historical Claims Duration, Year Four | 19.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Five | 14.80%
Short-duration Insurance Contracts, Historical Claims Duration, Year Six | 7.90%
Short-duration Insurance Contracts, Historical Claims Duration, Year Seven | 5.70%
Short-duration Insurance Contracts, Historical Claims Duration, Year Eight | 3.50%
Short-duration Insurance Contracts, Historical Claims Duration, Year Nine | 3.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Ten | 2.00%

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