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Transactions With Related Parties (Details) - USD ($) $ in Thousands | 3 Months Ended | 9 Months Ended |  |  |  |  |
--- | --- | --- | --- | --- | --- | --- | ---
Sep. 30, 2021 | Sep. 30, 2020 | Sep. 30, 2021 | Sep. 30, 2020 | Jun. 30, 2021 | Jan. 01, 2021 | Dec. 31, 2020 | Jun. 30, 2020 | Dec. 31, 2019
Related Party Transaction [Line Items] |  |  |  |  |  |  |  |  |
Reinsurance recoverable on unpaid and paid losses and loss adjustment expenses | $ 5,358,852 | $ 4,621,937 | $ 5,358,852 | $ 4,621,937 | $ 4,314,515 |  | $ 4,500,802 | $ 4,363,507 | $ 4,346,816
Ceded Premiums Written | 1,131,486 | $ 806,888 | 2,907,002 | $ 2,151,853 |  |  |  |  |
Reinsurance balances payable | 1,403,929 |  | 1,403,929 |  |  |  | 683,263 |  |
Operating affilicates | Watford Holdings Ltd |  |  |  |  |  |  |  |  |
Related Party Transaction [Line Items] |  |  |  |  |  |  |  |  |
Reinsurance recoverable on unpaid and paid losses and loss adjustment expenses | 874,900 |  | 874,900 |  |  |  |  |  |
Senior notes, face amount | $ 35,000 |  | $ 35,000 |  |  |  |  |  |
Senior notes, stated percentage | 6.50% |  | 6.50% |  |  |  |  |  |
Ceded Premiums Written | $ 316,200 |  |  |  |  |  |  |  |
Reinsurance balances payable | 281,200 |  | $ 281,200 |  |  |  |  |  |
Operating affilicates | Watford Holdings Ltd | Non-cumulative preferred shares |  |  |  |  |  |  |  |  |
Related Party Transaction [Line Items] |  |  |  |  |  |  |  |  |
Ownership percentage |  |  | 6.60% |  |  |  |  |  |
Operating affilicates | Premia Holdings Ltd |  |  |  |  |  |  |  |  |
Related Party Transaction [Line Items] |  |  |  |  |  |  |  |  |
Legacy business, amount of liabilities transferred |  |  |  |  |  | $ 380,000 |  |  |
Reinsurance recoverable on unpaid and paid losses and loss adjustment expenses | 0 |  | $ 0 |  |  |  | 199,800 |  |
Funds held liability | $ 8,800 |  | $ 8,800 |  |  |  | $ 149,600 |  |

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