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Third-Party Reinsurance - Effects of Reinsurance (Details) - USD ($) $ in Millions | 12 Months Ended
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Dec. 31, 2021 | Dec. 31, 2020 | Dec. 31, 2019
Earned premiums: |  |  |
Net earned premiums | $ 664.2 | $ 22.8 | $ 16.3
Ark |  |  |
Written premiums: |  |  |
Direct | 1,058.7 |  |
Ceded | (199.6) |  |
Net written premiums | 859.1 |  |
Earned premiums: |  |  |
Direct | 886.4 |  |
Ceded | (249.1) |  |
Net earned premiums | 637.3 |  |
Losses and LAE: |  |  |
Gross | 442.9 |  |
Ceded | (128.1) |  |
Net Losses and LAE | $ 314.8 |  |

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