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Transactions With Related Parties (Details) - USD ($) $ in Thousands | Jun. 30, 2021 | Mar. 31, 2021 | Jan. 01, 2021 | Dec. 31, 2020 | Jun. 30, 2020 | Mar. 31, 2020 | Dec. 31, 2019
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Related Party Transaction [Line Items] |  |  |  |  |  |  |
Reinsurance recoverable on unpaid and paid losses and LAE | $ 4,314,515 | $ 4,041,076 |  | $ 4,500,802 | $ 4,363,507 | $ 4,303,135 | $ 4,346,816
Premia Holdings Ltd. | Barbican Group Holdings Limited |  |  |  |  |  |  |
Related Party Transaction [Line Items] |  |  |  |  |  |  |
Legacy business, amount of liabilities transferred |  |  | $ 380,000 |  |  |  |
Reinsurance recoverable on unpaid and paid losses and LAE | 0 |  |  | 199,800 |  |  |
Funds held liability | $ 9,900 |  |  | $ 149,600 |  |  |

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- Definition Amount, after valuation allowance, recoverable under reinsurance contracts. Examples include, but are not limited to, settled and unsettled claims, incurred but not reported losses, loss adjustment expense, policy benefits and policy reserves. Excludes premiums paid under reinsurance contracts. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 310 -Section 45 -Paragraph 6 -URI http://asc.fasb.org/extlink&oid=99404803&loc=d3e21412-158489 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 310 -Section 45 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=99404803&loc=d3e21409-158489 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 20 -Section 50 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=99397103&loc=d3e6824-158387 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 825 -Section 50 -Paragraph 1B -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=123600520&loc=SL75241803-196195 + Details
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