Segment Information (Tables)

3 Months Ended

Mar. 31, 2025

Segment Reporting [Abstract]

Financial Information with Respect to Reporting Segments

Summarized below is financial information with respect to the Company’s reporting segments.

	Three Months Ended
	March 31, 2025
(in millions)		Core Commercial				Specialty				Personal Lines				Other				Total
Operating revenues:
Premiums	$		541.0		$		339.6		$		627.9		$		—		$		1,508.5
Net investment income			48.0				24.3				30.5				3.3				106.1
Fees and other income			1.3				1.3				3.7				0.1				6.4
Total operating revenues	$		590.3		$		365.2		$		662.1		$		3.4				1,621.0
Net realized and unrealized investment losses																			(17.8	)
Total revenues																	$		1,603.2
Operating income (loss) before interest expense    and income taxes:
Net premiums earned	$		541.0		$		339.6		$		627.9		$		—		$		1,508.5
Losses and LAE:
Current accident year losses and LAE			334.2				173.3				372.2				—				879.7
Prior year favorable development,    excluding catastrophes			(1.3	)			(15.9	)			(2.8	)			—				(20.0	)
Current year catastrophe losses			54.5				17.2				35.9				—				107.6
Prior year favorable catastrophe development			(8.5	)			(2.5	)			(1.0	)			—				(12.0	)
Total losses and LAE			378.9				172.1				404.3				—				955.3
Amortization of deferred acquisition costs and other    underwriting expenses(1)			182.1				126.3				161.9				—				470.3
Underwriting income (loss)			(20.0	)			41.2				61.7				—				82.9
Net investment income			48.0				24.3				30.5				3.3				106.1
Fees and other income			1.3				1.3				3.7				0.1				6.4
Other segment items(2)			(2.5	)			(2.2	)			(1.7	)			(2.6	)			(9.0	)
Operating income before interest expense    and income taxes	$		26.8		$		64.6		$		94.2		$		0.8				186.4
Interest on debt																			(8.5	)
Operating income before income taxes																			177.9
Non-operating income (loss) items:
Net realized and unrealized investment losses																			(17.8	)
Income before income taxes																	$		160.1

(1)Includes expenses directly incurred by each reporting segment, as well as corporate and other general expenses that are allocated using a consistent and reasonable approach, generally based on net premiums earned.

(2)Other segment items in Core Commercial, Specialty and Personal Lines primarily includes uncollectible premium charge-offs and non-insurance agency operating expenses, whereas other segment items in the Other segment includes operating costs related to certain of THG’s former life insurance businesses, including defined benefit pension-related costs, as well as holding company expenses.

	Three Months Ended
	March 31, 2024
(in millions)		Core Commercial				Specialty				Personal Lines				Other				Total
Operating revenues:
Premiums	$		528.9		$		320.9		$		598.8		$		—		$		1,448.6
Net investment income			40.8				20.3				25.6				3.0				89.7
Fees and other income			1.3				1.3				4.0				0.7				7.3
Total operating revenues	$		571.0		$		342.5		$		628.4		$		3.7				1,545.6
Net realized and unrealized investment gains																			5.5
Total revenues																	$		1,551.1
Operating income (loss) before interest expense    and income taxes:
Net premiums earned	$		528.9		$		320.9		$		598.8		$		—		$		1,448.6
Losses and LAE:
Current accident year losses and LAE			309.4				156.6				392.7				—				858.7
Prior year favorable development,    excluding catastrophes			(9.2	)			(1.1	)			(0.1	)			—				(10.4	)
Current year catastrophe losses			24.5				10.2				59.2				—				93.9
Prior year favorable catastrophe development			(3.8	)			(3.2	)			—				—				(7.0	)
Total losses and LAE			320.9				162.5				451.8				—				935.2
Amortization of deferred acquisition costs and other    underwriting expenses(1)			177.1				119.5				156.1				—				452.7
Underwriting income (loss)			30.9				38.9				(9.1	)			—				60.7
Net investment income			40.8				20.3				25.6				3.0				89.7
Fees and other income			1.3				1.3				4.0				0.7				7.3
Other segment items(2)			(1.5	)			(1.7	)			(1.6	)			(3.2	)			(8.0	)
Operating income before interest expense    and income taxes	$		71.5		$		58.8		$		18.9		$		0.5				149.7
Interest on debt																			(8.5	)
Operating income before income taxes																			141.2
Non-operating income (loss) items:
Net realized and unrealized investment gains																			5.5
Other non-operating items																			(1.4	)
Income before income taxes																	$		145.3

(1)Includes expenses directly incurred by each reporting segment, as well as corporate and other general expenses that are allocated using a consistent and reasonable approach, generally based on net premiums earned.

(2)Other segment items in Core Commercial, Specialty and Personal Lines primarily includes uncollectible premium charge-offs and non-insurance agency operating expenses, whereas other segment items in the Other segment includes operating costs related to certain of THG’s former investment and life insurance businesses, including defined benefit pension-related costs, as well as holding company expenses.

Identifiable Assets by Business Segment

The following table provides identifiable assets for the Company’s segments and discontinued operations:

(in millions)	March 31, 2025		December 31, 2024
Property and Casualty	$	15,384.6	$	15,188.8
Assets of discontinued businesses		85.7		85.7
Total	$	15,470.3	$	15,274.5