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Segment Information (Tables)

9 Months Ended

Sep. 30, 2025

Segment Reporting [Abstract]

Reconciliation of operating results by reportable segment

The following tables present the Company's operating results by reportable segment:

			Three Months Ended September 30,
			2025																		2024
			Property & Casualty						Other						Total						Property & Casualty						Other						Total
			(Amounts in millions)
Net premiums earned			$	1,403.0					$	7.4					$	1,410.4					$	1,313.3					$	7.4					$	1,320.7
Less:
Losses			735.3						3.8						739.1						782.4						3.8						786.2
Loss adjustment expenses			143.2						0.5						143.7						131.6						0.6						132.2
Losses and loss adjustment expenses			878.5						4.3						882.8						914.0						4.4						918.4
Policy acquisition costs			231.8						4.4						236.2						226.3						4.0						230.3
Other operating expenses			107.6						0.9						108.5						85.9						0.9						86.8
Underwriting gain (loss)			185.1						(2.2)						182.9						87.1						(1.9)						85.2
Investment income															84.0																		72.7
Net realized investment gains															84.5																		114.4
Other income															6.1																		22.5
Interest expense															(7.2)																		(7.7)
Pre-tax income															$	350.3																	$	287.1
Net income															$	280.4																	$	230.9

			Nine Months Ended September 30,
			2025																		2024
			Property & Casualty						Other						Total						Property & Casualty						Other						Total
			(Amounts in millions)
Net premiums earned			$	4,038.1					$	22.1					$	4,060.2					$	3,701.3					$	22.1					$	3,723.4
Less:
Losses			2,594.2						11.4						2,605.6						2,361.5						11.3						2,372.8
Loss adjustment expenses			436.5						1.5						438.0						384.9						1.4						386.3
Losses and loss adjustment expenses			3,030.7						12.9						3,043.6						2,746.4						12.7						2,759.1
Policy acquisition costs			682.6						10.2						692.8						620.2						9.8						630.0
Other operating expenses			281.7						2.3						284.0						243.3						2.3						245.6
Underwriting gain (loss)			43.1						(3.3)						39.8						91.4						(2.7)						88.7
Investment income															244.2																		206.7
Net realized investment gains															131.3																		155.5
Other income															21.1																		23.8
Interest expense															(21.6)																		(23.3)
Pre-tax income															$	414.8																	$	451.4
Net income															$	338.5																	$	366.9

Schedule direct premiums attributable to segment

The following tables present the Company’s net premiums earned and direct premiums written by reportable segment and line of insurance business:

			Three Months Ended September 30,
			2025																		2024
			Property & Casualty						Other						Total						Property & Casualty						Other						Total
			(Amounts in millions)
Private passenger automobile			$	900.0					$	—					$	900.0					$	854.4					$	—					$	854.4
Homeowners			334.2						—						334.2						301.8						—						301.8
Commercial automobile			96.1						—						96.1						97.3						—						97.3
Other			72.7						7.4						80.1						59.8						7.4						67.2
Net premiums earned			$	1,403.0					$	7.4					$	1,410.4					$	1,313.3					$	7.4					$	1,320.7
Private passenger automobile			$	919.9					$	—					$	919.9					$	878.2					$	—					$	878.2
Homeowners			446.6						—						446.6						370.2						—						370.2
Commercial automobile			91.8						—						91.8						95.8						—						95.8
Other			96.6						6.8						103.4						114.7						6.8						121.5
Direct premiums written			$	1,554.9					$	6.8					$	1,561.7					$	1,458.9					$	6.8					$	1,465.7

			Nine Months Ended September 30,
			2025																		2024
			Property & Casualty						Other						Total						Property & Casualty						Other						Total
			(Amounts in millions)
Private passenger automobile			$	2,646.0					$	—					$	2,646.0					$	2,408.3					$	—					$	2,408.3
Homeowners			907.1						—						907.1						852.3						—						852.3
Commercial automobile			287.3						—						287.3						280.7						—						280.7
Other			197.7						22.1						219.8						160.0						22.1						182.1
Net premiums earned			$	4,038.1					$	22.1					$	4,060.2					$	3,701.3					$	22.1					$	3,723.4
Private passenger automobile			$	2,707.9					$	—					$	2,707.9					$	2,551.3					$	—					$	2,551.3
Homeowners			1,225.3						—						1,225.3						1,034.2						—						1,034.2
Commercial automobile			292.2						—						292.2						298.6						—						298.6
Other			245.1						21.7						266.8						249.8						20.2						270.0
Direct premiums written			$	4,470.5					$	21.7					$	4,492.2					$	4,133.9					$	20.2					$	4,154.1

X

- Definition

Disclosure of direct premium written by line of business.

+ References

No definition available.

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- Definition

Tabular disclosure of the reconciliation of profit (loss) from reportable segments to the consolidated income (loss) before income tax expense (benefit) and discontinued operations. Includes, but is not limited to, reconciliation after income tax if income tax is allocated to the reportable segment.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 31
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-31

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 30
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-30

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