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Unpaid Loss and Loss Adjustment Expense - Additional Information (Details) - USD ($) |  |  | 6 Months Ended | 9 Months Ended | 12 Months Ended
--- | --- | --- | --- | --- | ---
Jul. 01, 2023 | Jul. 01, 2022 | Jun. 30, 2021 | Sep. 30, 2023 | Sep. 30, 2022 | Jun. 30, 2022
Effects of Reinsurance [Line Items] |  |  |  |  |  |
Favorable development on net loss and LAE reserves |  |  |  | $ (3,600,000) | $ (1,100,000) |
Current accident year incurred loss and LAE |  |  |  | $ 219,000,000.0 | $ 106,900,000 |
Reinsurance program, minimum losses threshold |  | $ 80,000,000 |  |  |  |
Reinsurance, per risk limit, amount | $ 750,000 |  |  |  |  |
Reinsurance, excess retention, amount reinsured, per event | 5,000,000 |  |  |  |  |
Reinsurance Contract [Axis]: Automatic Facultative Property Per Risk Excess of Loss | Lemonade Insurance Company |  |  |  |  |  |
Effects of Reinsurance [Line Items] |  |  |  |  |  |
Reinsurance, excess retention, amount reinsured, per policy | 3,000,000 |  |  |  |  |
Reinsurance Contract [Axis]: Automatic Facultative Property Per Risk Excess of Loss Reinsurance | Lemonade Insurance Company |  |  |  |  |  |
Effects of Reinsurance [Line Items] |  |  |  |  |  |
Reinsurance, excess retention, amount reinsured, per policy | $ 10,000,000 |  |  |  |  |
Reinsurance, excess retention, percentage | 100.00% |  |  |  |  |
Reinsurance Contract [Axis]: Excess of Loss Reinsurance Contract |  |  |  |  |  |
Effects of Reinsurance [Line Items] |  |  |  |  |  |
Initial limit for each loss occurrence | $ 50,000,000 |  |  |  |  |
Reinsurance, excess retention, amount reinsured, per event | 80,000,000 |  |  |  |  |
Reinsurance Contract [Axis]: Premiums and Losses to Reinsurers |  |  |  |  |  |
Effects of Reinsurance [Line Items] |  |  |  |  |  |
Reinsurance, reinsured risk, percentage |  |  |  | 30.00% |  |
Reinsurance Contract [Axis]: Property Per Risk Excess of Loss Reinsurance |  |  |  |  |  |
Effects of Reinsurance [Line Items] |  |  |  |  |  |
Reinsurance, excess retention, amount reinsured, per policy | $ 2,250,000 |  |  |  |  |
Reinsurance, excess retention, percentage | 100.00% |  |  |  |  |
Reinsurance Contract [Axis]: Property Per Risk Excess of Loss Reinsurance | Maximum |  |  |  |  |  |
Effects of Reinsurance [Line Items] |  |  |  |  |  |
Reinsurance, excess retention, amount reinsured, per policy | $ 750,000 |  |  |  |  |
Reinsurance Contract [Axis]: Proportional Reinsurance Contracts |  |  |  |  |  |
Effects of Reinsurance [Line Items] |  |  |  |  |  |
Percent of contracts subject to participation through reinsurance | 55.00% | 55.00% | 75.00% |  |  | 70.00%
Winter Storm Elliot |  |  |  |  |  |
Effects of Reinsurance [Line Items] |  |  |  |  |  |
Current accident year incurred loss and LAE |  |  |  | $ 10,000,000 |  |
Texas Hail Storm |  |  |  |  |  |
Effects of Reinsurance [Line Items] |  |  |  |  |  |
Current accident year incurred loss and LAE |  |  |  | $ 3,500,000 |  |

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