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Summary of Significant Accounting Policies Summary of Significant Accounting Policies (Tables) | 12 Months Ended
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Dec. 31, 2023
Accounting Policies [Abstract] |
Summary of Deferred Policy Acquisition Cost Amortization and Net Advertising Expense | The table below presents a summary of deferred policy acquisition cost amortization and net advertising expense:
| Year Ended December 31,
| 2023 |  | 2022 |  | 2021
| (Amounts in millions)
Deferred policy acquisition cost amortization | $ | 708.5 |  |  | $ | 654.6 |  |  | $ | 633.4 |
Net advertising expense | 8.9 |  |  | 11.8 |  |  | 50.1 |
Effects of Reinsurance | The effect of reinsurance on property and casualty premiums written and earned was as follows:
| Year Ended December 31,
| 2023 |  | 2022 |  | 2021
| (Amounts in thousands)
Premiums Written |  |  |  |  |
Direct | $ | 4,531,942 |  |  | $ | 4,018,057 |  |  | $ | 3,877,476 |
Ceded | (109,644) |  |  | (81,256) |  |  | (65,521) |
Assumed | 15,353 |  |  | 10,743 |  |  | 13,361 |
Net | $ | 4,437,651 |  |  | $ | 3,947,544 |  |  | $ | 3,825,316 |
Premiums Earned |  |  |  |  |
Direct | $ | 4,339,333 |  |  | $ | 3,993,771 |  |  | $ | 3,764,626 |
Ceded | (109,445) |  |  | (80,950) |  |  | (65,017) |
Assumed | 15,481 |  |  | 10,821 |  |  | 13,301 |
Net | $ | 4,245,369 |  |  | $ | 3,923,642 |  |  | $ | 3,712,910 |
Premium Receivable, Allowance for Credit Loss | The following table presents a summary of changes in allowance for credit losses on premiums receivable:
|  | Year Ended December 31,
|  | 2023 |  | 2022 |  | 2021
Beginning balance |  | $ | 5,800 |  |  | $ | 6,000 |  |  | $ | 10,000 |
Provision during the period for expected credit losses |  | 2,819 |  |  | 4,213 |  |  | (893) |
Write-off amounts during the period |  | (3,879) |  |  | (5,027) |  |  | (3,693) |
Recoveries during the period of amounts previously written off |  | 560 |  |  | 614 |  |  | 586 |
Ending balance |  | $ | 5,300 |  |  | $ | 5,800 |  |  | $ | 6,000 |
Reinsurance Recoverable, Allowance for Credit Loss | The following table presents a summary of changes in allowance for credit losses on reinsurance recoverables:
|  | Year Ended December 31,
|  | 2023 |  | 2022 |  | 2021
Beginning balance |  | $ | — |  |  | $ | — |  |  | $ | 91 |
Provision during the period for expected credit losses |  | 12 |  |  | — |  |  | (91) |
Write-off amounts during the period |  | — |  |  | — |  |  | — |
Recoveries during the period of amounts previously written off |  | — |  |  | — |  |  | — |
Ending balance |  | $ | 12 |  |  | $ | — |  |  | $ | — |

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