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Loss and Loss Adjustment Expense Reserves - TPC Participation (Details) | Dec. 31, 2021 | Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015 | Dec. 31, 2014 | Dec. 31, 2013 | Dec. 31, 2012
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Ark | Amount attributable to TPC Providers |  |  |  |  |  |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |  |  |  |  |  |
Percent of underwriting capital provided by third parties | 0.00% | 42.80% | 58.30% | 57.60% | 60.00% | 59.60% | 70.00% | 66.20% | 0.00% | 0.00%

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