Investments, Debt and Equity Securities [Abstract]

Investments Classified by Contractual Maturity Date

The amortized cost and fair value by maturity periods for fixed maturities are shown in the following table. Actual maturities may differ from contractual maturities because borrowers may have the right to call or prepay obligations with or without call or prepayment penalties, or the Company may have the right to put or sell the obligations back to the issuers.


DECEMBER 31	2025
(in millions)	Amortized Cost, net of Allowance for Credit Losses		Fair Value
Due in one year or less	$	127.5	$	127.5
Due after one year through five years		2,361.7		2,351.2
Due after five years through ten years		2,839.6		2,788.0
Due after ten years		314.9		292.7
		5,643.7		5,559.4
Mortgage-backed and other asset-backed securities		4,042.0		3,977.1
Total fixed maturities	$	9,685.7	$	9,536.5

Schedule of Unrealized Loss on Investments

The following tables provide information about the Company’s available-for-sale fixed maturity securities that were in an unrealized loss position at December 31, 2025 and 2024, including the length of time the securities have been in an unrealized loss position:


DECEMBER 31, 2025	12 months or less				Greater than 12 months				Total
(in millions)	Gross				Gross				Gross
	Unrealized		Fair		Unrealized		Fair		Unrealized		Fair
	Losses		Value		Losses		Value		Losses		Value
Investment grade:
U.S. Treasury and government agencies	$	—	$	11.9	$	38.2	$	319.7	$	38.2	$	331.6
Municipals		0.6		56.3		66.6		550.3		67.2		606.6
Corporates		1.0		271.3		51.2		704.2		52.2		975.5
Residential mortgage-backed		0.5		128.7		82.3		521.7		82.8		650.4
Commercial mortgage-backed		0.5		122.5		20.0		284.3		20.5		406.8
Other asset-backed		0.5		82.9		0.2		24.3		0.7		107.2
Total investment grade		3.1		673.6		258.5		2,404.5		261.6		3,078.1
Below investment grade:
Corporates		2.2		37.5		2.6		34.8		4.8		72.3
Commercial mortgage-backed		—		—		0.8		4.9		0.8		4.9
Other asset-backed		—		1.3		—		—		—		1.3
Total below investment grade		2.2		38.8		3.4		39.7		5.6		78.5
Total fixed maturities	$	5.3	$	712.4	$	261.9	$	2,444.2	$	267.2	$	3,156.6


DECEMBER 31, 2024	12 months or less				Greater than 12 months				Total
(in millions)	Gross				Gross				Gross
	Unrealized		Fair		Unrealized		Fair		Unrealized		Fair
	Losses		Value		Losses		Value		Losses		Value
Investment grade:
U.S. Treasury and government agencies	$	7.8	$	194.4	$	51.0	$	240.8	$	58.8	$	435.2
Municipals		3.0		132.5		106.2		680.9		109.2		813.4
Corporates		22.8		1,360.3		132.0		1,523.3		154.8		2,883.6
Residential mortgage-backed		16.5		896.8		139.8		747.2		156.3		1,644.0
Commercial mortgage-backed		0.7		23.7		41.4		485.4		42.1		509.1
Other asset-backed		2.5		181.4		0.8		78.5		3.3		259.9
Total investment grade		53.3		2,789.1		471.2		3,756.1		524.5		6,545.2
Below investment grade:
Foreign governments		—		0.1		—		—		—		0.1
Corporates		1.3		70.8		5.3		49.8		6.6		120.6
Commercial mortgage-backed		—		—		—		0.8		—		0.8
Total below investment grade		1.3		70.9		5.3		50.6		6.6		121.5
Total fixed maturities	$	54.6	$	2,860.0	$	476.5	$	3,806.7	$	531.1	$	6,666.7

Schedule of Amortized Cost of Mortgage Loan Participations by Credit Ratings and Year of Origination

The amortized cost of mortgage loan participations by credit ratings and year of origination was as follows:


DECEMBER 31, 2025
(in millions)	Prior to 2021		2021		2022		2023		2024		2025		Total
Credit Quality
Aaa/Aa/A	$	87.0	$	42.5	$	10.0	$	—	$	—	$	—	$	139.5
Baa		43.7		11.7		—		—		9.9		9.4		74.7
Ba and lower		32.0		—		—		—		8.9		—		40.9
Amortized cost	$	162.7	$	54.2	$	10.0	$	—	$	18.8	$	9.4	$	255.1
Allowance for credit losses														(8.1	)
Amortized cost, net of allowance for credit losses													$	247.0