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v3.20.4

Summary of Significant Accounting Policies - Effects of Reinsurance (Details) - USD ($) $ in Thousands | 3 Months Ended | 12 Months Ended
--- | --- | ---
Dec. 31, 2020 | Sep. 30, 2020 | Jun. 30, 2020 | Mar. 31, 2020 | Dec. 31, 2019 | Sep. 30, 2019 | Jun. 30, 2019 | Mar. 31, 2019 | Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
Premiums Written |  |  |  |  |  |  |  |  |  |  |
Direct |  |  |  |  |  |  |  |  | $ 3,654,200 | $ 3,774,600 | $ 3,550,900
Net |  |  |  |  |  |  |  |  | 3,610,000 | 3,730,000 | 3,500,000
Premiums Earned |  |  |  |  |  |  |  |  |  |  |
Direct |  |  |  |  |  |  |  |  | 3,603,780 | 3,655,233 | 3,416,687
Ceded |  |  |  |  |  |  |  |  | (56,212) | (56,725) | (48,941)
Assumed |  |  |  |  |  |  |  |  | 8,067 | 910 | 665
Net | $ 921,860 | $ 899,304 | $ 811,897 | $ 922,574 | $ 925,384 | $ 915,012 | $ 888,776 | $ 870,245 | 3,555,635 | 3,599,418 | 3,368,411
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |  |  |  |
Direct premiums written |  |  |  |  |  |  |  |  | 3,654,200 | 3,774,600 | 3,550,900
Net |  |  |  |  |  |  |  |  | 3,610,000 | 3,730,000 | 3,500,000
Direct amounts |  |  |  |  |  |  |  |  | 3,603,780 | 3,655,233 | 3,416,687
Ceded premiums |  |  |  |  |  |  |  |  | 56,212 | 56,725 | 48,941
Assumed |  |  |  |  |  |  |  |  | 8,067 | 910 | 665
Net premiums earned | $ 921,860 | $ 899,304 | $ 811,897 | $ 922,574 | $ 925,384 | $ 915,012 | $ 888,776 | $ 870,245 | 3,555,635 | 3,599,418 | 3,368,411
Property and Casualty Lines [Member] |  |  |  |  |  |  |  |  |  |  |
Premiums Written |  |  |  |  |  |  |  |  |  |  |
Direct |  |  |  |  |  |  |  |  | 3,624,965 | 3,742,627 | 3,524,186
Ceded |  |  |  |  |  |  |  |  | (50,630) | (43,785) | (55,973)
Assumed |  |  |  |  |  |  |  |  | 8,012 | 919 | 689
Net |  |  |  |  |  |  |  |  | 3,582,347 | 3,699,761 | 3,468,902
Premiums Earned |  |  |  |  |  |  |  |  |  |  |
Direct |  |  |  |  |  |  |  |  | 3,574,898 | 3,626,857 | 3,386,192
Ceded |  |  |  |  |  |  |  |  | (56,212) | (56,725) | (48,941)
Assumed |  |  |  |  |  |  |  |  | 8,067 | 910 | 665
Net |  |  |  |  |  |  |  |  | 3,526,753 | 3,571,042 | 3,337,916
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |  |  |  |
Direct premiums written |  |  |  |  |  |  |  |  | 3,624,965 | 3,742,627 | 3,524,186
Ceded |  |  |  |  |  |  |  |  | 50,630 | 43,785 | 55,973
Assumed |  |  |  |  |  |  |  |  | 8,012 | 919 | 689
Net |  |  |  |  |  |  |  |  | 3,582,347 | 3,699,761 | 3,468,902
Direct amounts |  |  |  |  |  |  |  |  | 3,574,898 | 3,626,857 | 3,386,192
Ceded premiums |  |  |  |  |  |  |  |  | 56,212 | 56,725 | 48,941
Assumed |  |  |  |  |  |  |  |  | 8,067 | 910 | 665
Net premiums earned |  |  |  |  |  |  |  |  | $ 3,526,753 | $ 3,571,042 | $ 3,337,916

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