Investments (Tables)

12 Months Ended

Dec. 31, 2023

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

Schedule of Unrealized Loss on Investments

An aging of unrealized losses on the Company’s Investments in Fixed Maturities at December 31, 2023 is presented below.

DOLLARS IN MILLIONS	Less Than 12 Months				12 Months or Longer				Total
	Fair Value		Unrealized Losses		Fair Value		Unrealized Losses		Fair Value		Unrealized Losses
Fixed Maturities:
U.S. Government and Government Agencies and Authorities	$	52.0	$	(0.8)	$	401.6	$	(83.7)	$	453.6	$	(84.5)
States and Political Subdivisions	112.9		(2.3)		928.3		(187.5)		1,041.2		(189.8)
Foreign Governments	—		—		1.9		(0.6)		1.9		(0.6)
Corporate Securities:
Bonds and Notes	198.4		(5.5)		2,813.0		(378.3)		3,011.4		(383.8)
Redeemable Preferred Stocks	—		—		7.9		(0.8)		7.9		(0.8)
Collateralized Loan Obligations	38.8		(0.4)		747.7		(24.1)		786.5		(24.5)
Other Mortgage- and Asset-backed	15.7		(0.1)		287.3		(46.2)		303.0		(46.3)
Total Fixed Maturities	$	417.8	$	(9.1)	$	5,187.7	$	(721.2)	$	5,605.5	$	(730.3)

An aging of unrealized losses on the Company’s Investments in Fixed Maturities at December 31, 2022 is presented below.

DOLLARS IN MILLIONS	Less Than 12 Months				12 Months or Longer				Total
	Fair Value		Unrealized Losses		Fair Value		Unrealized Losses		Fair Value		Unrealized Losses
Fixed Maturities:
U.S. Government and Government Agencies and Authorities	$	337.3	$	(49.3)	$	126.5	$	(36.5)	$	463.8	$	(85.8)
States and Political Subdivisions	854.7		(140.6)		276.8		(97.7)		1,131.5		(238.3)
Foreign Governments	0.1		—		2.6		(0.9)		2.7		(0.9)
Corporate Securities:
Bonds and Notes	2,730.6		(373.9)		424.4		(125.8)		3,155.0		(499.7)
Redeemable Preferred Stocks	7.7		(1.0)		—		—		7.7		(1.0)
Collateralized Loan Obligations	568.2		(34.2)		373.9		(26.6)		942.1		(60.8)
Other Mortgage- and Asset-backed	205.4		(28.9)		79.5		(21.4)		284.9		(50.3)
Total Fixed Maturities	$	4,704.0	$	(627.9)	$	1,283.7	$	(308.9)	$	5,987.7	$	(936.8)

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

The following table sets forth the change in allowance for credit losses on fixed maturities available-for-sale by major security type for year ended December 31, 2023.

	States and Political Subdivisions		Corporate Bonds and Notes		Total
(Dollars in Millions)
Beginning of the Year	$	0.7	$	8.9	$	9.6
Additions for Securities for which No Previous Expected Credit Losses were    Recognized	—		2.9		2.9
Reductions due to Sales	—		(2.6)		(2.6)
Net Increase (Decrease) in Allowance on Securities for which Expected Credit Losses were Previously Recognized	0.2		(1.1)		(0.9)
Write-offs Charged Against Allowance	(0.4)		(0.4)		(0.8)
End of the Year	$	0.5	$	7.7	$	8.2

The following table sets forth the change in allowance for credit losses on fixed maturities available-for-sale by major security type for year ended December 31, 2022.

	States and Political Subdivisions		Corporate Bonds and Notes		Total
(Dollars in Millions)
Beginning of the Year	$	—	$	7.5	$	7.5
Additions for Securities for which No Previous Expected Credit Losses were    Recognized	0.7		6.3		7.0
Net Increase in Allowance on Securities for which Expected Credit Losses were Previously Recognized	—		5.8		5.8
Write-offs Charged Against Allowance	—		(10.7)		(10.7)
End of the Year	$	0.7	$	8.9	$	9.6

Schedule of Other Investments

The carrying values of the Company’s Other Investments at December 31, 2023 and 2022 were:

DOLLARS IN MILLIONS	2023		2022
Equity Securities at Modified Cost	$	32.6	$	38.4
Convertible Securities at Fair Value	—		43.3
Real Estate at Depreciated Cost	94.7		93.6
Mortgage Loans	99.8		91.1
Other	14.8		3.5
Total	$	241.9	$	269.9

Investments in Fixed Maturities

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

Schedule of Available-for-sale Securities Reconciliation

The amortized cost and estimated fair values of the Company’s Investments in Fixed Maturities at December 31, 2023 were:

DOLLARS IN MILLIONS	Amortized Cost		Gross Unrealized				Allowance for Expected Credit Losses		Fair Value
			Gains		Losses
U.S. Government and Government Agencies and Authorities	$	594.1	$	1.9	$	(84.5)	$	—	$	511.5
States and Political Subdivisions	1,575.9		16.3		(189.8)		(0.5)		1,401.9
Foreign Governments	4.4		—		(0.6)		—		3.8
Corporate Securities:
Bonds and Notes	4,046.8		35.5		(383.8)		(7.7)		3,690.8
Redeemable Preferred Stocks	9.0		0.1		(0.8)		—		8.3
Collateralized Loan Obligations	973.6		0.7		(24.5)		—		949.8
Other Mortgage- and Asset-backed	362.0		0.1		(46.3)		—		315.8
Investments in Fixed Maturities	$	7,565.8	$	54.6	$	(730.3)	$	(8.2)	$	6,881.9

The amortized cost and estimated fair values of the Company’s Investments in Fixed Maturities at December 31, 2022 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	$	612.5	$	1.3	$	(85.8)	$	—	$	528.0
States and Political Subdivisions	1,797.6		10.3		(238.3)		(0.7)		1,568.9
Foreign Governments	5.0		—		(0.9)		—		4.1
Corporate Securities:
Bonds and Notes	4,030.3		17.7		(499.7)		(8.9)		3,539.4
Redeemable Preferred Stocks	9.0		—		(1.0)		—		8.0
Collateralized Loan Obligations	1,014.7		—		(60.8)		—		953.9
Other Mortgage- and Asset-backed	342.7		0.1		(50.3)		—		292.5
Investments in Fixed Maturities	$	7,811.8	$	29.4	$	(936.8)	$	(9.6)	$	6,894.8

Investments Classified by Contractual Maturity Date

The amortized cost and estimated fair values of the Company’s Investments in Fixed Maturities at December 31, 2023 by contractual maturity were:

DOLLARS IN MILLIONS	Amortized Cost		Fair Value
Due in One Year or Less	$	173.8	$	169.9
Due after One Year to Five Years	903.0		876.3
Due after Five Years to Ten Years	1,069.5		940.1
Due after Ten Years	3,615.5		3,235.4
Mortgage- and Asset-backed Securities Not Due at a Single Maturity Date	1,804.0		1,660.2
Investments in Fixed Maturities	$	7,565.8	$	6,881.9