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v3.20.1

Segment Information - Summary of Premiums Written and Earned by Segment (Details) - USD ($) $ in Thousands | 3 Months Ended
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Mar. 31, 2020 | Mar. 31, 2019
Segment Reporting Information [Line Items] |  |
Net premiums earned | $ 922,574 | $ 870,245
Direct Premiums Written | 957,900 | 922,100
Private Passenger Automobile Line [Member] |  |
Segment Reporting Information [Line Items] |  |
Net premiums earned | 693,900 | 672,600
Direct Premiums Written | 710,400 | 705,300
Homeowners Line [Member] |  |
Segment Reporting Information [Line Items] |  |
Net premiums earned | 139,500 | 119,300
Direct Premiums Written | 147,500 | 130,900
Commercial Automobile Line [Member] |  |
Segment Reporting Information [Line Items] |  |
Net premiums earned | 55,200 | 49,600
Direct Premiums Written | 61,700 | 54,400
Other [Member] |  |
Segment Reporting Information [Line Items] |  |
Net premiums earned | 34,000 | 28,700
Direct Premiums Written | 38,300 | 31,500
Property and Casualty Lines [Member] |  |
Segment Reporting Information [Line Items] |  |
Net premiums earned | 915,400 | 863,100
Direct Premiums Written | 949,700 | 915,300
Property and Casualty Lines [Member] | Private Passenger Automobile Line [Member] |  |
Segment Reporting Information [Line Items] |  |
Net premiums earned | 693,900 | 672,600
Direct Premiums Written | 710,400 | 705,300
Property and Casualty Lines [Member] | Homeowners Line [Member] |  |
Segment Reporting Information [Line Items] |  |
Net premiums earned | 139,500 | 119,300
Direct Premiums Written | 147,500 | 130,900
Property and Casualty Lines [Member] | Commercial Automobile Line [Member] |  |
Segment Reporting Information [Line Items] |  |
Net premiums earned | 55,200 | 49,600
Direct Premiums Written | 61,700 | 54,400
Property and Casualty Lines [Member] | Other [Member] |  |
Segment Reporting Information [Line Items] |  |
Net premiums earned | 26,800 | 21,600
Direct Premiums Written | 30,100 | 24,700
Other Segments [Member] |  |
Segment Reporting Information [Line Items] |  |
Net premiums earned | 7,200 | 7,100
Direct Premiums Written | 8,200 | 6,800
Other Segments [Member] | Private Passenger Automobile Line [Member] |  |
Segment Reporting Information [Line Items] |  |
Net premiums earned | 0 | 0
Direct Premiums Written | 0 | 0
Other Segments [Member] | Homeowners Line [Member] |  |
Segment Reporting Information [Line Items] |  |
Net premiums earned | 0 | 0
Direct Premiums Written | 0 | 0
Other Segments [Member] | Commercial Automobile Line [Member] |  |
Segment Reporting Information [Line Items] |  |
Net premiums earned | 0 | 0
Direct Premiums Written | 0 | 0
Other Segments [Member] | Other [Member] |  |
Segment Reporting Information [Line Items] |  |
Net premiums earned | 7,200 | 7,100
Direct Premiums Written | $ 8,200 | $ 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 http://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 http://asc.fasb.org/extlink&oid=114873790&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 http://asc.fasb.org/extlink&oid=34713774&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 http://asc.fasb.org/extlink&oid=114873765&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 http://asc.fasb.org/extlink&oid=6486672&loc=d3e27261-158547 + Details
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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
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