Segment Information - Narrative (Details) - business	9 Months Ended
Sep. 30, 2021	Sep. 30, 2020
Segment Reporting Information [Line Items]
Number of businesses	3
Gross Written Premiums \| Geographic Concentration Risk \| Michigan, Florida, Texas and Pennsylvania
Segment Reporting Information [Line Items]
Concentration risk	51.40%	49.90%

For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
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Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
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Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
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