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v3.23.1

Segment Information - Summary of Premiums Written and Earned by Segment (Details) - USD ($) $ in Thousands | 3 Months Ended
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Mar. 31, 2023 | Mar. 31, 2022
Segment Reporting Information [Line Items] |  |
Net premiums earned | $ 1,004,704 | $ 962,550
Direct premiums written | 1,018,600 | 1,018,200
Private passenger automobile |  |
Segment Reporting Information [Line Items] |  |
Net premiums earned | 660,600 | 659,300
Direct premiums written | 634,300 | 681,300
Homeowners |  |
Segment Reporting Information [Line Items] |  |
Net premiums earned | 222,500 | 192,000
Direct premiums written | 241,600 | 210,200
Commercial automobile |  |
Segment Reporting Information [Line Items] |  |
Net premiums earned | 69,100 | 64,500
Direct premiums written | 80,000 | 71,600
Other |  |
Segment Reporting Information [Line Items] |  |
Net premiums earned | 52,500 | 46,800
Direct premiums written | 62,700 | 55,100
Property & Casualty |  |
Segment Reporting Information [Line Items] |  |
Net premiums earned | 997,562 | 955,418
Direct premiums written | 1,012,238 | 1,011,385
Property & Casualty | Private passenger automobile |  |
Segment Reporting Information [Line Items] |  |
Net premiums earned | 660,600 | 659,300
Direct premiums written | 634,300 | 681,300
Property & Casualty | Homeowners |  |
Segment Reporting Information [Line Items] |  |
Net premiums earned | 222,500 | 192,000
Direct premiums written | 241,600 | 210,200
Property & Casualty | Commercial automobile |  |
Segment Reporting Information [Line Items] |  |
Net premiums earned | 69,100 | 64,500
Direct premiums written | 80,000 | 71,600
Property & Casualty | Other |  |
Segment Reporting Information [Line Items] |  |
Net premiums earned | 45,400 | 39,600
Direct premiums written | 56,300 | 48,300
Other |  |
Segment Reporting Information [Line Items] |  |
Net premiums earned | 7,100 | 7,200
Direct premiums written | 6,400 | 6,800
Other | Private passenger automobile |  |
Segment Reporting Information [Line Items] |  |
Net premiums earned | 0 | 0
Direct premiums written | 0 | 0
Other | Homeowners |  |
Segment Reporting Information [Line Items] |  |
Net premiums earned | 0 | 0
Direct premiums written | 0 | 0
Other | Commercial automobile |  |
Segment Reporting Information [Line Items] |  |
Net premiums earned | 0 | 0
Direct premiums written | 0 | 0
Other | Other |  |
Segment Reporting Information [Line Items] |  |
Net premiums earned | 7,100 | 7,200
Direct premiums written | $ 6,400 | $ 6,800

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- Definition Amount, before premiums ceded to other entities and premiums assumed by the entity, of premiums written. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 605 -Section 50 -Paragraph 1 -Subparagraph (b)(1) -URI https://asc.fasb.org/extlink&oid=6486672&loc=d3e27261-158547 + Details
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- Definition Amount, after premiums ceded to other entities and premiums assumed by the entity, of premiums earned. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 220 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-04(1)) -URI https://asc.fasb.org/extlink&oid=120400993&loc=SL114874131-224263 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 235 -Section S99 -Paragraph 2 -Subparagraph (SX 210.12-17(Column E)) -URI https://asc.fasb.org/extlink&oid=120401096&loc=d3e574992-122915 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 220 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-04(13)(c)) -URI https://asc.fasb.org/extlink&oid=120399700&loc=SL114874048-224260 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 605 -Section 50 -Paragraph 1 -Subparagraph (c)(3) -URI https://asc.fasb.org/extlink&oid=6486672&loc=d3e27261-158547 + Details
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