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Loss and Loss Adjustment Expense Reserves - LAE Reserve Activity (Details) - USD ($) $ in Millions | 12 Months Ended
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Dec. 31, 2023 | Dec. 31, 2022 | Dec. 31, 2021
Losses and LAE incurred relating to: |  |  |
Net incurred losses and LAE | $ 726.8 | $ 536.4 | $ 314.8
Ark |  |  |
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward] |  |  |
Gross beginning balance | 1,296.5 | 894.7 | 696.0
Less: beginning reinsurance recoverable on unpaid losses | (505.0) | (428.9) | (433.4)
Net loss and LAE reserves | 791.5 | 465.8 | 262.6
Losses and LAE incurred relating to: |  |  |
Current Year | 706.9 | 588.1 | 336.3
Prior Year | 19.9 | (51.7) | (21.5)
Net incurred losses and LAE | 726.8 | 536.4 | 314.8
Loss and LAE paid relating to: |  |  |
Current year losses | (51.3) | (98.9) | (43.9)
Prior year losses | (356.6) | (158.6) | (61.6)
Net paid losses and LAE | (407.9) | (257.5) | (105.5)
Change in TPC providers’ participation | 145.4 | 57.5 | (2.2)
Foreign currency translation and other adjustments to loss and LAE reserves | 8.5 | (10.7) | (3.9)
Net ending balance | 1,264.3 | 791.5 | 465.8
Plus: ending reinsurance recoverable on unpaid losses | (340.8) | (505.0) | (428.9)
Gross ending balance | 1,605.1 | 1,296.5 | 894.7
Ark | Amount attributable to TPC Providers |  |  |
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward] |  |  |
Less: beginning reinsurance recoverable on unpaid losses | (145.4) | (276.8) | (319.2)
Loss and LAE paid relating to: |  |  |
Plus: ending reinsurance recoverable on unpaid losses | $ (0.0) | $ (145.4) | $ (276.8)

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- Definition The amount needed to reflect the estimated ultimate cost of settling claims relating to insured events that have occurred on or before the balance sheet date, whether or not reported to the insurer at that date. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 944 -SubTopic 40 -Name Accounting Standards Codification -Section 50 -Paragraph 3 -Subparagraph (cc) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480081/944-40-50-3 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 50 -Paragraph 3 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480081/944-40-50-3 + Details
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- Definition Amount, after effects of reinsurance, of payments to settle claims incurred in the current period and related claims settlement costs. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Section 50 -Paragraph 3 -Subparagraph (c) -SubTopic 40 -Topic 944 -Publisher FASB -URI https://asc.fasb.org//1943274/2147480081/944-40-50-3 + Details
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- Definition Amount, after effects of reinsurance, of payments to settle claims incurred in prior periods and related claims settlement costs. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Section 50 -Paragraph 3 -Subparagraph (c) -SubTopic 40 -Topic 944 -Publisher FASB -URI https://asc.fasb.org//1943274/2147480081/944-40-50-3 + Details
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- Definition Amount of foreign currency gain (loss) which decreases (increases) the cost of settling unpaid claims after deduction of reinsurance recoveries. Includes, but is not limited to, claims which have been incurred but not reported. + References No definition available. + Details
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- Definition Liability as of the balance sheet date for amounts representing estimated cost of settling unpaid claims under the terms of the underlying insurance policies, less estimated reinsurance recoveries on such claims. This includes an estimate for claims which have been incurred but not reported. Claim adjustment expenses represent the costs estimated to be incurred in the settlement of unpaid claims. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 944 -SubTopic 210 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03(a)(13)(a)(1)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147479440/944-210-S99-1 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 944 -SubTopic 40 -Name Accounting Standards Codification -Section 50 -Paragraph 3 -Subparagraph (cc) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480081/944-40-50-3 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 50 -Paragraph 3 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480081/944-40-50-3 + Details
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