Investments (Tables)

9 Months Ended

Sep. 30, 2024

Investments, Debt and Equity Securities [Abstract]

Schedule of Amortized Cost, Gross Unrealized Gains and Losses, Fair Value of Fixed Maturity Security

The following tables show the cost or amortized cost, allowance for credit losses, gross unrealized gains and losses, and fair value of the Company’s fixed maturity securities as of the dates indicated:

	September 30, 2024
	Cost or Amortized Cost		Allowance for Credit Losses		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value
Fixed maturity securities:
U.S. government and government agencies and authorities	$	61.4	$	—	$	0.9	$	(2.9)	$	59.4
States, municipalities and political subdivisions	132.3		—		1.9		(7.7)		126.5
Foreign governments	501.1		—		5.4		(13.0)		493.5
Asset-backed	970.2		—		9.1		(9.0)		970.3
Commercial mortgage-backed	356.1		—		2.8		(33.7)		325.2
Residential mortgage-backed	656.9		—		5.6		(38.4)		624.1
U.S. corporate	3,501.9		—		83.8		(152.6)		3,433.1
Foreign corporate	1,586.5		—		36.7		(59.2)		1,564.0
Total fixed maturity securities	$	7,766.4	$	—	$	146.2	$	(316.5)	$	7,596.1

	December 31, 2023
	Cost or Amortized Cost		Allowance for Credit Losses		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value
Fixed maturity securities:
U.S. government and government agencies and authorities	$	68.9	$	—	$	0.7	$	(4.4)	$	65.2
States, municipalities and political subdivisions	159.2		—		1.2		(11.2)		149.2
Foreign governments	483.1		—		9.4		(12.7)		479.8
Asset-backed	891.4		—		5.2		(22.8)		873.8
Commercial mortgage-backed	383.1		—		0.4		(53.3)		330.2
Residential mortgage-backed	534.7		—		1.9		(50.6)		486.0
U.S. corporate	3,300.5		—		45.3		(215.4)		3,130.4
Foreign corporate	1,471.5		—		17.6		(91.6)		1,397.5
Total fixed maturity securities	$	7,292.4	$	—	$	81.7	$	(462.0)	$	6,912.1

Schedule of Amortized Cost and Fair Value of Fixed Maturity Securities by Contractual Maturity

The cost or amortized cost and fair value of fixed maturity securities as of September 30, 2024 by contractual maturity are shown below. Actual maturities may differ from contractual maturities because issuers of the securities may have the right to call or prepay obligations with or without call or prepayment penalties.

	Cost or Amortized Cost		Fair Value
Due in one year or less	$	202.6	$	202.1
Due after one year through five years	1,488.1		1,492.8
Due after five years through ten years	2,980.7		2,969.8
Due after ten years	1,111.8		1,011.8
Total	5,783.2		5,676.5
Asset-backed	970.2		970.3
Commercial mortgage-backed	356.1		325.2
Residential mortgage-backed	656.9		624.1
Total	$	7,766.4	$	7,596.1

Schedule of Gain (Loss) on Securities

The following table sets forth the net realized gains (losses) on investments and fair value changes to equity securities, including impairments, recognized in the consolidated statements of operations for the periods indicated: 

	Three Months Ended September 30,				Nine Months Ended September 30,
	2024		2023		2024		2023
Net realized (losses) gains on investments related to sales and other and fair value changes to equity securities:
Fixed maturity securities	$	(18.5)	$	(14.1)	$	(47.7)	$	(25.9)
Equity securities (1)	11.2		(3.0)		21.3		(15.9)
Commercial mortgage loans on real estate	(0.1)		(1.3)		(2.4)		(2.6)
Other investments	(1.5)		0.1		3.3		1.1
Total net realized losses on investments related to sales and other and fair value changes to equity securities	(8.9)		(18.3)		(25.5)		(43.3)
Net realized losses related to impairments:
Fixed maturity securities	(0.2)		(0.8)		(1.2)		(2.9)
Other investments	(9.2)		—		(20.0)		(3.5)
Total net realized losses related to impairments	(9.4)		(0.8)		(21.2)		(6.4)
Total net realized losses on investments and fair value changes to equity securities	$	(18.3)	$	(19.1)	$	(46.7)	$	(49.7)

(1)Upward adjustments of $2.5 million, $6.6 million, $0.2 million and $0.6 million for the three and nine months ended September 30, 2024 and 2023 and impairments of $9.2 million, $20.0 million, $0.0 million and $3.5 million for the three and nine months ended September 30, 2024 and 2023, respectively, were realized on equity investments accounted for under the measurement alternative.

Schedule of Fair Value Changes to Equity Securities

The following table sets forth the portion of fair value changes to equity securities held for the periods indicated:

	Three Months Ended September 30,				Nine Months Ended September 30,
	2024		2023		2024		2023
Net gains (losses) recognized on equity securities	$	11.2	$	(3.0)	$	21.3	$	(15.9)
Less: Net realized gains (losses) related to sales of equity securities	1.4		0.1		6.5		(2.2)
Total fair value changes to equity securities held	$	9.8	$	(3.1)	$	14.8	$	(13.7)

Schedule of Equity Securities without Readily Determinable Fair Value

The following table summarizes information related to these investments:

	September 30, 2024		December 31, 2023
Initial cost	$	72.8	$	86.8
Cumulative upward adjustments	57.7		51.1
Cumulative downward adjustments (including impairments)	(21.4)		(17.9)
Carrying value	$	109.1	$	120.0

Schedule of Duration of Gross Unrealized Losses on Fixed Maturity Securities and Equity Securities

The investment category and duration of the Company’s gross unrealized losses on fixed maturity securities as of September 30, 2024 and December 31, 2023 were as follows:

	September 30, 2024
	Less than 12 months				12 Months or More				Total
	Fair Value		Unrealized Losses		Fair Value		Unrealized Losses		Fair Value		Unrealized Losses
Fixed maturity securities:
U.S. government and government agencies and authorities	$	—	$	—	$	33.0	$	(2.9)	$	33.0	$	(2.9)
States, municipalities and political subdivisions	4.8		(0.2)		77.9		(7.5)		82.7		(7.7)
Foreign governments	93.4		(2.9)		183.8		(10.1)		277.2		(13.0)
Asset-backed	48.2		(2.3)		98.0		(6.7)		146.2		(9.0)
Commercial mortgage-backed	13.0		(1.5)		215.4		(32.2)		228.4		(33.7)
Residential mortgage-backed	55.6		(1.1)		239.1		(37.3)		294.7		(38.4)
U.S. corporate	198.5		(9.8)		1,136.1		(142.8)		1,334.6		(152.6)
Foreign corporate	64.7		(2.3)		540.6		(56.9)		605.3		(59.2)
Total fixed maturity securities	$	478.2	$	(20.1)	$	2,523.9	$	(296.4)	$	3,002.1	$	(316.5)

	December 31, 2023
	Less than 12 months				12 Months or More				Total
	Fair Value		Unrealized Losses		Fair Value		Unrealized Losses		Fair Value		Unrealized Losses
Fixed maturity securities:
U.S. government and government agencies and authorities	$	5.2	$	(0.1)	$	43.7	$	(4.3)	$	48.9	$	(4.4)
States, municipalities and political subdivisions	3.9		(0.1)		96.5		(11.1)		100.4		(11.2)
Foreign governments	42.5		(0.5)		203.5		(12.2)		246.0		(12.7)
Asset-backed	64.0		(3.0)		404.7		(19.8)		468.7		(22.8)
Commercial mortgage-backed	66.3		(8.4)		244.2		(44.9)		310.5		(53.3)
Residential mortgage-backed	98.8		(3.5)		285.1		(47.1)		383.9		(50.6)
U.S. corporate	331.9		(14.7)		1,596.4		(200.7)		1,928.3		(215.4)
Foreign corporate	153.9		(5.6)		744.8		(86.0)		898.7		(91.6)
Total fixed maturity securities	$	766.5	$	(35.9)	$	3,618.9	$	(426.1)	$	4,385.4	$	(462.0)

Schedule of Credit Quality Indicators for Commercial Mortgage Loans

The following table presents the amortized cost basis of commercial mortgage loans, excluding the allowance for credit losses, by origination year for certain key credit quality indicators at September 30, 2024 and December 31, 2023.

	September 30, 2024
	Origination Year
	2024		2023		2022		2021		2020		Prior		Total		% of Total
Loan to value ratios (1):
70% and less	$	32.9	$	47.1	$	33.1	$	21.1	$	—	$	60.4	$	194.6	58.0	%
71% to 80%	3.8		4.9		27.3		65.5		2.8		4.4		108.7		32.4	%
81% to 95%	—		—		12.8		10.1		—		5.2		28.1		8.4	%
Greater than 95%	—		—		4.0		—		—		—		4.0		1.2	%
Total	$	36.7	$	52.0	$	77.2	$	96.7	$	2.8	$	70.0	$	335.4	100.0	%

	September 30, 2024
	Origination Year
	2024		2023		2022		2021		2020		Prior		Total		% of Total
Debt-service coverage ratios (2):
Greater than 2.0	$	2.0	$	0.6	$	18.0	$	10.9	$	—	$	43.0	$	74.5	22.2	%
1.5 to 2.0	11.3		5.8		16.9		27.3		—		11.7		73.0		21.8	%
1.0 to 1.5	22.4		23.8		18.0		28.7		—		6.2		99.1		29.5	%
Less than 1.0	1.0		21.8		24.3		29.8		2.8		9.1		88.8		26.5	%
Total	$	36.7	$	52.0	$	77.2	$	96.7	$	2.8	$	70.0	$	335.4	100.0	%

	December 31, 2023
	Origination Year
	2023		2022		2021		2020		2019		Prior		Total		% of Total
Loan to value ratios (1):
70% and less	$	49.6	$	42.3	$	29.5	$	—	$	—	$	60.1	$	181.5	54.6	%
71% to 80%	2.5		22.7		69.6		2.8		—		4.4		102.0		30.7	%
81% to 95%	—		10.7		25.5		—		—		5.5		41.7		12.5	%
Greater than 95%	—		2.0		1.3		—		—		4.1		7.4		2.2	%
Total	$	52.1	$	77.7	$	125.9	$	2.8	$	—	$	74.1	$	332.6	100.0	%

	December 31, 2023
	Origination Year
	2023		2022		2021		2020		2019		Prior		Total		% of Total
Debt-service coverage ratios (2):
Greater than 2.0	$	—	$	11.8	$	9.3	$	—	$	—	$	44.9	$	66.0	19.8	%
1.5 to 2.0	18.9		23.6		28.7		—		—		12.2		83.4		25.1	%
1.0 to 1.5	33.2		18.2		40.1		—		—		7.1		98.6		29.7	%
Less than 1.0	—		24.1		47.8		2.8		—		9.9		84.6		25.4	%
Total	$	52.1	$	77.7	$	125.9	$	2.8	$	—	$	74.1	$	332.6	100.0	%

(1)Loan-to-value ratio derived from current principal amount of the loan divided by the fair value of the property. The fair value of the underlying commercial properties is updated at least annually.

(2)Debt-service coverage ratio calculated using most recently reported annual net operating income from property operators divided by annual debt service payments.