Investments (Tables)

12 Months Ended

Dec. 31, 2024

Investments, Debt and Equity Securities [Abstract]

Amortized Cost and Fair Values of Securities by Security Type

At December 31, 2024 and 2023, all fixed maturity securities were classified as available-for-sale. The amortized cost and fair values of securities by security type are shown as follows:

	December 31, 2024
	Amortized Cost, Gross of ACL1		ACL1		Gross Unrealized Gain		Gross Unrealized Loss		Fair Value
	(in millions of dollars)
United States Government and Government Agencies and Authorities	$	544.6	$	—	$	13.9	$	28.0	$	530.5
States, Municipalities, and Political Subdivisions	3,795.6		—		65.5		569.7		3,291.4
Foreign Governments	912.1		—		9.5		153.5		768.1
Public Utilities	5,525.0		—		132.3		364.4		5,292.9
Mortgage/Asset-Backed Securities2	949.4		—		5.0		37.2		917.2
All Other Corporate Bonds	26,535.2		2.8		450.6		2,160.8		24,822.2
Redeemable Preferred Stocks	8.0		—		—		0.4		7.6
Total Fixed Maturity Securities	$	38,269.9	$	2.8	$	676.8	$	3,314.0	$	35,629.9

	December 31, 2023
	Amortized Cost, Gross of ACL1		ACL1		Gross Unrealized Gain		Gross Unrealized Loss		Fair Value
	(in millions of dollars)
United States Government and Government Agencies and Authorities	$	618.6	$	—	$	25.3	$	19.1	$	624.8
States, Municipalities, and Political Subdivisions	4,041.3		—		135.3		498.2		3,678.4
Foreign Governments	982.1		—		29.8		121.2		890.7
Public Utilities	5,398.2		—		217.1		293.7		5,321.6
Mortgage/Asset-Backed Securities2	658.0		—		10.1		24.0		644.1
All Other Corporate Bonds	26,708.4		2.2		771.8		1,807.3		25,670.7
Redeemable Preferred Stocks	4.0		—		—		0.4		3.6
Total Fixed Maturity Securities	$	38,410.6	$	2.2	$	1,189.4	$	2,763.9	$	36,833.9

1 Allowance for Credit Losses

2Includes credit-tranched securities collateralized by loan obligations, auto loans, and other asset types

Schedule of Unrealized Loss on Investments

The following charts indicate the length of time our fixed maturity securities have been in a gross unrealized loss position.

	December 31, 2024
	Less Than 12 Months				12 Months or Greater
	Fair Value		Gross Unrealized Loss		Fair Value		Gross Unrealized Loss
	(in millions of dollars)
United States Government and Government Agencies and Authorities	$	43.7	$	4.1	$	201.3	$	23.9
States, Municipalities, and Political Subdivisions	425.8		15.3		1,926.2		554.4
Foreign Governments	171.9		10.6		266.3		142.9
Public Utilities	1,281.7		48.4		1,549.5		316.0
Mortgage/Asset-Backed Securities1	199.9		8.9		285.9		28.3
All Other Corporate Bonds	4,904.4		182.5		12,209.3		1,978.3
Redeemable Preferred Stocks	3.9		0.1		3.7		0.3
Total Fixed Maturity Securities	$	7,031.3	$	269.9	$	16,442.2	$	3,044.1

	December 31, 2023
	Less Than 12 Months				12 Months or Greater
	Fair Value		Gross Unrealized Loss		Fair Value		Gross Unrealized Loss
	(in millions of dollars)
United States Government and Government Agencies and Authorities	$	118.8	$	0.7	$	197.3	$	18.4
States, Municipalities, and Political Subdivisions	128.0		4.0		2,035.1		494.2
Foreign Governments	149.9		3.3		312.9		117.9
Public Utilities	373.7		10.4		1,720.6		283.3
Mortgage/Asset-Backed Securities1	60.3		2.5		316.7		21.5
All Other Corporate Bonds	1,483.8		26.8		14,215.2		1,780.5
Redeemable Preferred Stocks	—		—		3.6		0.4
Total Fixed Maturity Securities	$	2,314.5	$	47.7	$	18,801.4	$	2,716.2

1Includes credit-tranched securities collateralized by loan obligations, auto loans, and other asset types

Distribution of the Maturity Dates for Fixed Maturity Securities

The following is a distribution of the maturity dates for fixed maturity securities. The maturity dates have not been adjusted for possible calls or prepayments.

	December 31, 2024
	Amortized Cost, Net of ACL1		Unrealized Gain Position				Unrealized Loss Position
			Gross Gain		Fair Value		Gross Loss		Fair Value
	(in millions of dollars)
1 year or less	$	1,484.1	$	4.1	$	432.4	$	6.2	$	1,049.6
Over 1 year through 5 years	7,688.2		123.5		2,840.8		196.6		4,774.3
Over 5 years through 10 years	8,404.6		236.4		3,486.1		565.5		4,589.4
Over 10 years	19,740.8		307.8		4,965.7		2,508.5		12,574.4
	37,317.7		671.8		11,725.0		3,276.8		22,987.7
Mortgage/Asset-Backed Securities2	949.4		5.0		431.4		37.2		485.8
Total Fixed Maturity Securities	$	38,267.1	$	676.8	$	12,156.4	$	3,314.0	$	23,473.5

	December 31, 2023
	Amortized Cost, Net of ACL1		Unrealized Gain Position				Unrealized Loss Position
			Gross Gain		Fair Value		Gross Loss		Fair Value
	(in millions of dollars)
1 year or less	$	935.0	$	0.9	$	140.8	$	7.5	$	787.6
Over 1 year through 5 years	7,594.4		128.2		2,685.7		179.0		4,857.9
Over 5 years through 10 years	9,430.3		372.1		4,100.0		610.8		5,091.6
Over 10 years	19,790.7		678.1		8,524.4		1,942.6		10,001.8
	37,750.4		1,179.3		15,450.9		2,739.9		20,738.9
Mortgage/Asset-Backed Securities2	658.0		10.1		267.1		24.0		377.0
Total Fixed Maturity Securities	$	38,408.4	$	1,189.4	$	15,718.0	$	2,763.9	$	21,115.9

1 Allowance for Credit Losses

2Includes credit-tranched securities collateralized by loan obligations, auto loans, and other asset types

Distribution by External Credit Rating for Fixed Maturity Securities

The following chart depicts an analysis of our fixed maturity security portfolio between investment-grade and below-investment-grade categories as of December 31, 2024:

					Gross Unrealized Loss
	Fair Value		Gross Unrealized Gain		Amount		Percent of Total Gross Unrealized Loss
	(in millions of dollars)
Investment-Grade	$	34,193.9	$	661.8	$	3,236.2	97.7	%
Below-Investment-Grade	1,436.0		15.0		77.8		2.3
Total Fixed Maturity Securities	$	35,629.9	$	676.8	$	3,314.0	100.0	%

Debt Securities, Available-for-sale, Allowance for Credit Loss

The following tables present a rollforward of the allowance for credit losses on available-for-sale fixed maturity securities, which were classified as "all other corporate bonds" during the years ended December 31, 2024 and December 31, 2023.

	Year Ended December 31
	2024		2023
	(in millions of dollars)
Balance, beginning of period	$	2.2	$	—
Credit losses on securities for which credit losses were not previously recorded	2.8		2.2
Change in allowance on securities with allowance recorded in previous period	0.2		—
Change in allowance due to securities sold during the period	(2.4)		—
Balance, end of period	$	2.8	$	2.2

Low Income Housing Tax Credits

The Company invests in tax credit partnerships primarily for the receipt of income tax credits and tax benefits derived from passive losses on the investments. Amounts recognized in the consolidated statements of income are as follows:

	Year Ended December 31
	2024		2023		2022
	(in millions of dollars)
Income Tax Credits	$	0.1	$	1.1	$	8.0
Amortization, Net of Tax	—		(0.5)		(5.9)
Income Tax Benefit	$	0.1	$	0.6	$	2.1

Mortgage Loans by Property Type and Geographic Region

The carrying amount of mortgage loans by property type and geographic region are presented below.

	December 31
	2024				2023
	(in millions of dollars)
	Carrying		Percent of		Carrying		Percent of
	Amount		Total		Amount		Total
Property Type
Apartment	$	658.2	29.6	%	$	685.8	29.6	%
Industrial	690.4		31.0		706.0		30.5
Office	338.4		15.2		379.9		16.4
Retail	496.2		22.3		503.9		21.7
Other	41.3		1.9		42.6		1.8
Total	$	2,224.5	100.0	%	$	2,318.2	100.0	%

Region
New England	$	52.6	2.4	%	$	55.1	2.4	%
Mid-Atlantic	167.2		7.5		155.1		6.7
East North Central	297.2		13.4		314.4		13.6
West North Central	151.1		6.8		163.5		7.0
South Atlantic	532.5		23.9		553.0		23.8
East South Central	95.1		4.3		110.7		4.8
West South Central	193.6		8.7		200.9		8.7
Mountain	278.7		12.5		282.7		12.2
Pacific	456.5		20.5		482.8		20.8
Total	$	2,224.5	100.0	%	$	2,318.2	100.0	%

Schedule of Participating Mortgage Loans by Internal Credit Rating and Loan to Value

The following tables present information about mortgage loans by the applicable internal quality indicators:

	December 31
	2024				2023
	(in millions of dollars)
	Carrying Amount		Percent of Total		Carrying Amount		Percent of Total
Internal Mortgage Rating
AA	$	117.8	5.3	%	$	85.2	3.7	%
A	1,099.1		49.4		942.5		40.6
BBB	915.5		41.2		1,249.5		53.9
BB	85.0		3.8		41.0		1.8
B	7.1		0.3		—		—
Total	$	2,224.5	100.0	%	$	2,318.2	100.0	%

Loan-to-Value Ratio1
<= 65%	$	1,639.6	73.8	%	$	1,409.9	60.8	%
> 65% <= 75%	367.6		16.5		707.0		30.5
> 75% <= 85%	152.3		6.8		136.5		5.9
> 85%	65.0		2.9		64.8		2.8
Total	$	2,224.5	100.0	%	$	2,318.2	100.0	%

1 Loan-to-Value Ratio utilizes the most recent internal valuation of the property

Mortgage Loans by Credit Quality Indicators

The following tables present the amortized cost of our mortgage loans by year of origination and internal quality indicators for the years ended December 31, 2024 and 2023:

	Year Ended December 31, 2024
	Prior to 2020		2020		2021		2022		2023		2024		Total
	(in millions of dollars)
Internal Mortgage Rating
AA	$	111.5	$	—	$	6.4	$	—	$	—	$	—	$	117.9
A	780.5		99.6		169.1		24.6		9.5		18.0		1,101.3
BBB	561.7		55.1		155.1		63.0		57.3		28.2		920.4
BB	86.8		—		—		—		—		—		86.8
B	14.2		—		—		—		—		—		14.2
Total Amortized Cost	1,554.7		154.7		330.6		87.6		66.8		46.2		2,240.6
Allowance for credit losses	(13.7)		(0.5)		(1.0)		(0.3)		(0.4)		(0.2)		(16.1)
Carrying Amount	$	1,541.0	$	154.2	$	329.6	$	87.3	$	66.4	$	46.0	$	2,224.5
Loan-to-Value Ratio1
<=65%	$	1,229.6	$	112.9	$	210.0	$	40.8	$	38.7	$	11.7	$	1,643.7
>65<=75%	154.1		33.7		72.1		46.8		28.1		34.5		369.3
>75%<=85%	126.4		8.1		20.1		—		—		—		154.6
>85%	44.6		—		28.4		—		—		—		73.0
Total Amortized Cost	1,554.7		154.7		330.6		87.6		66.8		46.2		2,240.6
Allowance for credit losses	(13.7)		(0.5)		(1.0)		(0.3)		(0.4)		(0.2)		(16.1)
Carrying Amount	$	1,541.0	$	154.2	$	329.6	$	87.3	$	66.4	$	46.0	$	2,224.5

1 Loan-to-Value Ratio utilizes the most recent internal valuation of the property

	Year Ended December 31, 2023
	Prior to 2019		2019		2020		2021		2022		2023		Total
	(in millions of dollars)
Internal Mortgage Rating
AA	$	74.3	$	11.0	$	—	$	—	$	—	$	—	$	85.3
A	589.0		100.3		94.1		100.1		23.2		38.0		944.7
BBB	618.4		224.8		71.4		248.0		64.4		29.2		1,256.2
BB	42.2		—		—		—		—		—		42.2
Total Amortized Cost	1,323.9		336.1		165.5		348.1		87.6		67.2		2,328.4
Allowance for credit losses	(6.3)		(1.3)		(0.6)		(1.0)		(0.6)		(0.4)		(10.2)
Carrying Amount	$	1,317.6	$	334.8	$	164.9	$	347.1	$	87.0	$	66.8	$	2,318.2
Loan-to-Value Ratio1
<=65%	$	908.3	$	197.7	$	116.4	$	145.2	$	16.2	$	30.0	$	1,413.8
>65<=75%	252.1		138.4		40.8		171.0		71.4		37.2		710.9
>75%<=85%	97.3		—		8.3		31.9		—		—		137.5
>85%	66.2		—		—		—		—		—		66.2
Total Amortized Cost	1,323.9		336.1		165.5		348.1		87.6		67.2		2,328.4
Allowance for credit losses	(6.3)		(1.3)		(0.6)		(1.0)		(0.6)		(0.4)		(10.2)
Carrying Amount	$	1,317.6	$	334.8	$	164.9	$	347.1	$	87.0	$	66.8	$	2,318.2

1 Loan-to-Value Ratio utilizes the most recent internal valuation of the property

Financing Receivable, Allowance for Credit Loss

The following tables present a rollforward of allowance for expected credit losses by loan-to-value ratio for the years ended December 31, 2024 and 2023:

	Year Ended December 31, 2024
	Beginning of Period		Current Period Provisions		Write-Offs		Recoveries		End of Period
	(in millions of dollars)
Loan-to-Value Ratio1
<=65%	$	3.8	$	0.4	$	—	$	—	$	4.2
>65<=75%	3.8		(2.1)		—		—		1.7
>75%<=85%	1.2		8.0		(7.0)		—		2.2
>85%	1.4		6.6		—		—		8.0
Total	$	10.2	$	12.9	$	(7.0)	$	—	$	16.1

	Year Ended December 31, 2023
	Beginning of Period		Current Period Provisions		Write-Offs		Recoveries		End of Period
	(in millions of dollars)
Loan-to-Value Ratio1
<=65%	$	3.0	$	0.8	$	—	$	—	$	3.8
>65<=75%	4.7		(0.9)		—		—		3.8
>75%<=85%	1.1		0.1		—		—		1.2
>85%	0.5		0.9		—		—		1.4
Total	$	9.3	$	0.9	$	—	$	—	$	10.2

1 Loan-to-Value Ratio utilizes the most recent internal valuation of the property

Remaining Contractual Maturity of Securities Lending Agreements

The remaining contractual maturities of our securities lending agreements disaggregated by class of collateral pledged are as follows:

	December 31
	2024		2023
	Overnight and Continuous
	(in millions of dollars)
Borrowings
Public Utilities	$	5.2	$	1.8
Short-Term Investments	1.0		—
All Other Corporate Bonds	56.5		61.3
Total Borrowings	$	62.7	$	63.1
Gross Amount of Recognized Liability for Securities Lending Transactions	62.7		63.1
Amounts Related to Agreements Not Included in Offsetting Disclosure Contained Herein	$	—	$	—

Federal Home Loan Bank Common Stock Carrying Amounts, Amounts Posted, and Advances Received

The carrying value of common stock owned, collateral posted, and advances received are as follows:

	December 31
	2024		2023
	(in millions of dollars)
Carrying Value of FHLB Common Stock	$	26.7	$	15.7
Advances from FHLB	324.2		64.5
Carrying Value of Collateral Posted to FHLB
Fixed Maturity Securities	$	553.6	$	589.0
Commercial Mortgage Loans	908.2		986.8
Total Carrying Value of Collateral Posted to FHLB	$	1,461.8	$	1,575.8

Schedule of Financial Instrument and Derivative Offsetting

Shown below are our financial instruments that either meet the accounting requirements that allow them to be offset in our balance sheets or that are subject to an enforceable master netting arrangement or similar agreement. Our accounting policy is to not offset these financial instruments in our balance sheets. Net amounts disclosed below have been reduced by the amount of collateral pledged to or received from our counterparties.

	December 31, 2024
	Gross Amount						Gross Amount Not
	of Recognized		Gross Amount		Net Amount		Offset in Balance Sheet
	Financial		Offset in		Presented in		Financial		Cash		Net
	Instruments		Balance Sheet		Balance Sheet		Instruments		Collateral		Amount
	(in millions of dollars)
Financial Assets:
Derivatives	$	79.4	$	—	$	79.4	$	(75.7)	$	(3.2)	$	0.5
Securities Lending	94.0		—		94.0		(31.3)		(62.7)		—
Total	$	173.4	$	—	$	173.4	$	(107.0)	$	(65.9)	$	0.5
Financial Liabilities:
Derivatives	$	255.7	$	—	$	255.7	$	(254.3)	$	—	$	1.4
Securities Lending	62.7		—		62.7		(62.7)		—		—
Total	$	318.4	$	—	$	318.4	$	(317.0)	$	—	$	1.4

	December 31, 2023
	Gross Amount						Gross Amount Not
	of Recognized		Gross Amount		Net Amount		Offset in Balance Sheet
	Financial		Offset in		Presented in		Financial		Cash		Net
	Instruments		Balance Sheet		Balance Sheet		Instruments		Collateral		Amount
	(in millions of dollars)
Financial Assets:
Derivatives	$	99.9	$	—	$	99.9	$	(91.9)	$	(6.4)	$	1.6
Securities Lending	72.0		—		72.0		(8.9)		(63.1)		—
Total	$	171.9	$	—	$	171.9	$	(100.8)	$	(69.5)	$	1.6
Financial Liabilities:
Derivatives	$	116.2	$	—	$	116.2	$	(109.4)	$	—	$	6.8
Securities Lending	63.1		—		63.1		(63.1)		—		—
Total	$	179.3	$	—	$	179.3	$	(172.5)	$	—	$	6.8

Net Investment Income

Net investment income reported in our consolidated statements of income is presented below.

	Year Ended December 31
	2024		2023		2022
	(in millions of dollars)
Fixed Maturity Securities	$	1,860.4	$	1,853.7	$	1,849.8
Derivatives	30.7		45.1		57.8
Mortgage Loans	88.6		92.5		101.5
Policy Loans	20.9		20.8		20.0
Other Long-term Investments
Perpetual Preferred Securities	0.3		2.5		5.0
Private Equity Partnerships1	103.1		78.1		110.1
Other	12.0		9.2		9.4
Short-term Investments	90.9		68.7		20.0
Gross Investment Income	2,206.9		2,170.6		2,173.6
Less Investment Expenses	65.2		61.8		39.4
Less Investment Income on Participation Fund Account Assets	11.7		12.1		12.0
Net Investment Income	$	2,130.0	$	2,096.7	$	2,122.2

1The net unrealized gain recognized in net investment income for the year ended December 31, 2024 related to private equity partnerships still held at December 31, 2024 was $127.1 million, reduced by net management fees and partnership expenses of $(24.0) million. For the years ended December 31, 2023 and 2022, the net unrealized gain recognized in net investment income related to private equity partnerships still held at year-end was $102.9 million and $124.1 million, respectively, reduced by net management fees and partnership expenses of $(24.8) million and $(14.0) million, respectively. See Note 2 for further discussion of private equity partnerships.

^[1]

Realized Investment Gains and Losses Reported in Consolidated Statements of Income

Investment gains and losses are as follows:

	Year Ended December 31
	2024		2023		2022
	(in millions of dollars)
Fixed Maturity Securities
Gross Gains on Sales	$	1.3	$	4.4	$	2.3
Gross Losses on Sales	(39.5)		(53.1)		(28.8)
Impairment Loss1	(2.5)		—		—
Change in Allowance for Credit Losses	(3.0)		(2.2)		(4.6)
Mortgage Loans and Other Invested Assets
Gross Gains on Sales	0.5		6.0		1.4
Gross Losses on Sales	—		(1.0)		—
Impairment Loss	(7.0)		(3.0)		—
Change in Allowance for Credit Losses	(5.9)		(0.9)		(1.0)
Embedded Derivative in Modified Coinsurance Arrangement	13.0		12.4		16.2
All Other Derivatives	3.8		(0.6)		2.6
Other	9.2		—		—
Foreign Currency Transactions	(4.5)		2.0		(3.8)
Net Investment (Loss)	$	(34.6)	$	(36.0)	$	(15.7)

1Includes write-down of securities that we intended to sell prior to recovery of the amortized cost basis.

[1] The net unrealized gain recognized in net investment income for the year ended December 31, 2024 related to private equity partnerships still held at December 31, 2024 was $127.1 million, reduced by net management fees and partnership expenses of $(24.0) million. For the years ended December 31, 2023 and 2022, the net unrealized gain recognized in net investment income related to private equity partnerships still held at year-end was $102.9 million and $124.1 million, respectively, reduced by net management fees and partnership expenses of $(24.8) million and $(14.0) million, respectively. See Note 2 for further discussion of private equity partnerships.