Investments (Tables)

3 Months Ended

Mar. 31, 2025

Debt Securities, Available-for-sale [Line Items]

Investments Classified by Contractual Maturity Date

The amortized cost and estimated fair values of the Company’s Investments in Fixed Maturities at March 31, 2025 by contractual maturity were:

(Dollars in Millions)	Amortized Cost		Fair Value
Due in One Year or Less	$	333.0	$	327.5
Due after One Year to Five Years	873.4		848.1
Due after Five Years to Ten Years	1,003.8		893.9
Due after Ten Years	3,474.0		2,915.8
Mortgage- and Asset-backed Securities Not Due at a Single Maturity Date	1,688.0		1,573.3
Investments in Fixed Maturities	$	7,372.2	$	6,558.6

Debt Securities, Available-for-Sale, Unrealized Loss Position, Fair Value

An aging of unrealized losses on the Company’s Investments in Fixed Maturities at March 31, 2025 is presented below.

	Less Than 12 Months				12 Months or Longer				Total
(Dollars in Millions)	Fair Value		Unrealized Losses		Fair Value		Unrealized Losses		Fair Value		Unrealized Losses
Fixed Maturities:
U.S. Government and Government Agencies and Authorities	$	17.5	$	(0.1)	$	390.1	$	(90.8)	$	407.6	$	(90.9)
States and Political Subdivisions	200.1		(7.6)		966.6		(209.5)		1,166.7		(217.1)
Foreign Governments	0.3		—		1.4		(0.2)		1.7		(0.2)
Corporate Securities:
Bonds and Notes	684.3		(30.1)		2,790.4		(445.9)		3,474.7		(476.0)
Redeemable Preferred Stocks	—		—		6.6		(0.9)		6.6		(0.9)
Collateralized Loan Obligations	175.9		(0.7)		92.2		(6.1)		268.1		(6.8)
Other Mortgage- and Asset-backed	44.0		(0.2)		268.4		(29.6)		312.4		(29.8)
Total Fixed Maturities	$	1,122.1	$	(38.7)	$	4,515.7	$	(783.0)	$	5,637.8	$	(821.7)

    

An aging of unrealized losses on the Company’s Investments in Fixed Maturities at December 31, 2024 is presented below.

	Less Than 12 Months				12 Months or Longer				Total
(Dollars in Millions)	Fair Value		Unrealized Losses		Fair Value		Unrealized Losses		Fair Value		Unrealized Losses
Fixed Maturities:
U.S. Government and Government Agencies and Authorities	$	41.7	$	(0.5)	$	383.6	$	(101.9)	$	425.3	$	(102.4)
States and Political Subdivisions	242.7		(10.3)		933.4		(215.1)		1,176.1		(225.4)
Foreign Governments	—		—		1.4		(0.2)		1.4		(0.2)
Corporate Securities:
Bonds and Notes	674.3		(40.9)		2,605.7		(477.9)		3,280.0		(518.8)
Redeemable Preferred Stocks	2.0		—		6.6		(1.0)		8.6		(1.0)
Collateralized Loan Obligations	34.2		(0.1)		89.5		(7.1)		123.7		(7.2)
Other Mortgage- and Asset-backed	12.0		(0.1)		261.7		(34.4)		273.7		(34.5)
Total Fixed Maturities	$	1,006.9	$	(51.9)	$	4,281.9	$	(837.6)	$	5,288.8	$	(889.5)

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

The Company monitors accrued interest and writes off amounts when they are not expected to be received.

	States and Political Subdivisions		Corporate Bonds and Notes		Total
(Dollars in Millions)
Balance, Beginning of Year	$	0.3	$	10.4	$	10.7
Reductions Due to Sales	—		(0.5)		(0.5)
Net (Decrease) Increase in Allowance on Securities for which Expected Credit Losses were Previously Recognized	(0.1)		0.3		0.2
Write-Offs Charged Against Allowance	—		(1.1)		(1.1)
Balance, End of Period	$	0.2	$	9.1	$	9.3

The following table sets forth the change in allowance for credit losses on fixed maturities available-for-sale by major security type for the three months ended March 31, 2024.

	States and Political Subdivisions		Corporate Bonds and Notes		Total
(Dollars in Millions)
Balance, Beginning of Year	$	0.5	$	7.7	$	8.2
Reductions Due to Sales	—		(0.2)		(0.2)
Net Decrease in Allowance on Securities for which Expected Credit Losses were Previously Recognized	—		(0.3)		(0.3)
Balance, End of Period	$	0.5	$	7.2	$	7.7

Schedule of Other Investments

The carrying values of the Company’s Other Investments at March 31, 2025 and December 31, 2024 were:

(Dollars in Millions)	Mar 31, 2025		Dec 31, 2024
Equity Securities at Modified Cost	$	21.7	$	22.5
Real Estate at Depreciated Cost	99.7		99.5
Mortgage Loans	103.1		75.3
Alternative Energy Partnership Investments	17.3		17.6
Other	2.7		2.2
Total Other Investments	$	244.5	$	217.1

Investment Income

Net Investment Income for the three months ended March 31, 2025 and 2024 was:

	Three Months Ended
(Dollars in Millions)	Mar 31, 2025		Mar 31, 2024
Investment Income:
Interest on Fixed Income Securities1	$	76.4	$	79.8
Dividends on Equity Securities Excluding Alternative Investments	0.8		2.8
Alternative Investments:
Equity Method Limited Liability Investments	(0.7)		(2.1)
Limited Liability Investments Included in Equity Securities	3.7		3.4
Total Alternative Investments	3.0		1.3
Short-term Investments	8.6		7.3
Loans to Policyholders	5.3		5.2
Real Estate	2.2		2.3
Company-Owned Life Insurance	10.2		7.1
Other	2.0		2.5
Total Investment Income	108.5		108.3
Investment Expenses:
Real Estate	2.1		2.2
Other Investment Expenses	5.2		5.7
Total Investment Expenses	7.3		7.9
Net Investment Income	$	101.2	$	100.4
1Reduced by interest expense incurred on FHLB borrowings used for spread lending purposes of $4.8 million and $5.2 million for the three months ended March 31, 2025 and 2024, respectively.

Schedule of Realized Gain (Loss)

Gross gains and losses on sales of investments in fixed maturities and gains and losses associated with Ultra-Long Treasury Futures for the three months ended March 31, 2025 and 2024 were:

	Three Months Ended
(Dollars in Millions)	Mar 31, 2025		Mar 31, 2024
Fixed Maturities:
Gains on Sales	$	1.3	$	12.8
Losses on Sales	(0.5)		(2.3)
Gains (Losses) on Hedging Activity	—		(7.9)

Investments in Fixed Maturities

Debt Securities, Available-for-sale [Line Items]

Schedule of Available-for-sale Securities Reconciliation

The amortized cost and fair values of the Company’s Investments in Fixed Maturities at March 31, 2025 were:

	Amortized Cost		Gross Unrealized				Allowance for Expected Credit Losses		Fair Value
(Dollars in Millions)			Gains		Losses
U.S. Government and Government Agencies and Authorities	$	601.0	$	1.7	$	(90.9)	$	—	$	511.8
States and Political Subdivisions	1,447.4		2.1		(217.1)		(0.2)		1,232.2
Foreign Governments	6.6		0.2		(0.2)		—		6.6
Corporate Securities:
Bonds and Notes	4,087.4		11.0		(476.0)		(7.1)		3,615.3
Redeemable Preferred Stocks	9.8		0.1		(0.9)		—		9.0
Collateralized Loan Obligations	796.3		1.8		(6.8)		(2.0)		789.3
Other Mortgage- and Asset-backed	423.7		0.5		(29.8)		—		394.4
Investments in Fixed Maturities	$	7,372.2	$	17.4	$	(821.7)	$	(9.3)	$	6,558.6

The amortized cost and fair values of the Company’s Investments in Fixed Maturities at December 31, 2024 were:

	Amortized Cost		Gross Unrealized				Allowance for Expected Credit Losses		Fair Value
(Dollars in Millions)			Gains		Losses
U.S. Government and Government Agencies and Authorities	$	588.6	$	0.6	$	(102.4)	$	—	$	486.8
States and Political Subdivisions	1,457.3		1.6		(225.4)		(0.3)		1,233.2
Foreign Governments	6.5		0.3		(0.2)		—		6.6
Corporate Securities:
Bonds and Notes	4,038.3		8.9		(518.8)		(8.8)		3,519.6
Redeemable Preferred Stocks	9.8		0.1		(1.0)		—		8.9
Collateralized Loan Obligations	747.8		2.5		(7.2)		(1.6)		741.5
Other Mortgage- and Asset-backed	446.7		0.8		(34.5)		—		413.0
Investments in Fixed Maturities	$	7,295.0	$	14.8	$	(889.5)	$	(10.7)	$	6,409.6