Debt Securities

9 Months Ended

Sep. 30, 2025

Debt Securities, Available-for-Sale [Abstract]

Note 3 – Debt Securities

Investments in debt securities, classified as available-for-sale, are as follows:


	Amortized		Gross unrealized					Estimated
(in millions)	cost		Gains		Losses			fair value
September 30, 2025
U.S. Treasury bonds	$	249.4	$	1.4	$	(1.9	)	$	248.9
Municipal bonds		961.2		8.8		(59.7	)		910.3
Foreign government bonds		226.5		1.8		(4.7	)		223.6
Governmental agency bonds		243.0		0.3		(7.6	)		235.7
Governmental agency mortgage-backed securities		5,257.2		31.6		(198.2	)		5,090.6
U.S. corporate debt securities		1,048.8		16.4		(15.0	)		1,050.2
Foreign corporate debt securities		483.7		10.4		(5.2	)		488.9
	$	8,469.8	$	70.7	$	(292.3	)	$	8,248.2
December 31, 2024
U.S. Treasury bonds	$	180.7	$	0.1	$	(5.2	)	$	175.6
Municipal bonds		844.9		5.3		(73.7	)		776.5
Foreign government bonds		217.1		1.6		(7.1	)		211.6
Governmental agency bonds		203.8		—		(14.0	)		189.8
Governmental agency mortgage-backed securities		4,844.4		1.7		(343.8	)		4,502.3
U.S. corporate debt securities		948.4		5.6		(28.4	)		925.6
Foreign corporate debt securities		491.6		5.3		(12.4	)		484.5
	$	7,730.9	$	19.6	$	(484.6	)	$	7,265.9

Sales of debt securities resulted in realized gains of $1.7 million and $4.2 million, realized losses of $3.7 million and $13.0 million and proceeds of $240.4 million and $747.4 million for the three and nine months ended September 30, 2025, respectively. Sales of debt securities resulted in realized gains of $20.3 million and $21.4 million, realized losses of $346.9 million and $352.4 million and proceeds of $4.6 billion and $4.9 billion for the three and nine months ended September 30, 2024, respectively.

Investments in debt securities in an unrealized loss position, and their respective length of time in such position, are as follows:


	Less than 12 months					12 months or longer					Total
(in millions)	Estimated fair value		Unrealized losses			Estimated fair value		Unrealized losses			Estimated fair value		Unrealized losses
September 30, 2025
U.S. Treasury bonds	$	79.3	$	(0.4	)	$	36.1	$	(1.5	)	$	115.4	$	(1.9	)
Municipal bonds		185.7		(4.8	)		380.7		(54.9	)		566.4		(59.7	)
Foreign government bonds		11.8		—			60.1		(4.7	)		71.9		(4.7	)
Governmental agency bonds		144.7		(1.3	)		29.4		(6.3	)		174.1		(7.6	)
Governmental agency mortgage-backed securities		1,533.5		(13.7	)		1,866.0		(184.5	)		3,399.5		(198.2	)
U.S. corporate debt securities		144.4		(1.4	)		107.8		(13.6	)		252.2		(15.0	)
Foreign corporate debt securities		44.8		(0.2	)		71.4		(5.0	)		116.2		(5.2	)
	$	2,144.2	$	(21.8	)	$	2,551.5	$	(270.5	)	$	4,695.7	$	(292.3	)
December 31, 2024
U.S. Treasury bonds	$	81.8	$	(1.8	)	$	52.9	$	(3.4	)	$	134.7	$	(5.2	)
Municipal bonds		248.3		(4.4	)		417.0		(69.3	)		665.3		(73.7	)
Foreign government bonds		29.8		(0.2	)		72.7		(6.9	)		102.5		(7.1	)
Governmental agency bonds		144.4		(5.3	)		37.9		(8.7	)		182.3		(14.0	)
Governmental agency mortgage-backed securities		2,977.2		(98.4	)		1,290.4		(245.4	)		4,267.6		(343.8	)
U.S. corporate debt securities		435.2		(9.6	)		117.5		(18.8	)		552.7		(28.4	)
Foreign corporate debt securities		159.4		(3.2	)		110.5		(9.2	)		269.9		(12.4	)
	$	4,076.1	$	(122.9	)	$	2,098.9	$	(361.7	)	$	6,175.0	$	(484.6	)

Based on the Company’s review of its debt securities in an unrealized loss position it determined that the losses were due to non-credit factors and, therefore, it does not consider these securities to be credit impaired at September 30, 2025. As of September 30, 2025, the Company did not intend to sell any debt securities in an unrealized loss position and it is not more likely than not that the Company will be required to sell any debt securities before recovery of their amortized cost basis.

In determining credit losses on its debt securities in an unrealized loss position, the Company considers certain factors that may include, among others, severity of the unrealized loss, security type, industry sector, credit rating, yield to maturity, profitability and stock performance.

In the normal course of operations, the Company may seek to optimize its investment portfolio and prospective investment returns by selling certain debt securities in an unrealized loss (or gain) position for which such unrealized loss (or gain) has been deferred in other comprehensive income. Sales of such debt securities could result in the realization of material losses (or gains) recorded in net income in the period the debt securities are sold.

Investments in debt securities at September 30, 2025, by contractual maturities, are as follows:


(in millions)	Due in one year or less		Due after one through five years		Due after five through ten years		Due after ten years		Total
U.S. Treasury bonds
Amortized cost	$	48.8	$	159.4	$	17.0	$	24.2	$	249.4
Estimated fair value	$	48.4	$	159.3	$	17.1	$	24.1	$	248.9
Municipal bonds
Amortized cost		7.9		105.3		375.9		472.1		961.2
Estimated fair value		7.9		103.9		349.3		449.2		910.3
Foreign government bonds
Amortized cost		24.8		148.7		49.4		3.6		226.5
Estimated fair value		24.8		147.9		48.0		2.9		223.6
Governmental agency bonds
Amortized cost		0.6		0.8		207.6		34.0		243.0
Estimated fair value		0.6		0.8		206.5		27.8		235.7
U.S. corporate debt securities
Amortized cost		11.6		544.1		393.6		99.5		1,048.8
Estimated fair value		11.5		548.7		398.7		91.3		1,050.2
Foreign corporate debt securities
Amortized cost		21.0		326.9		103.5		32.3		483.7
Estimated fair value		21.0		331.4		105.9		30.6		488.9
Total debt securities (excluding mortgage-backed securities)
Amortized cost	$	114.7	$	1,285.2	$	1,147.0	$	665.7	$	3,212.6
Estimated fair value	$	114.2	$	1,292.0	$	1,125.5	$	625.9	$	3,157.6
Total mortgage-backed securities
Amortized cost										5,257.2
Estimated fair value										5,090.6
Total debt securities
Amortized cost									$	8,469.8
Estimated fair value									$	8,248.2

Mortgage-backed securities, which include contractual terms to maturity, are not categorized by contractual maturity as borrowers may have the right to call or prepay obligations with, or without, call or prepayment penalties.

The composition of the debt securities portfolio at September 30, 2025, by credit rating, is as follows:


	A- or higher					BBB+ to BBB-					Non-Investment Grade					Total
(dollars in millions)	Estimated fair value		Percentage			Estimated fair value		Percentage			Estimated fair value		Percentage			Estimated fair value
U.S. Treasury bonds	$	248.9		100.0	%	$	—		—	%	$	—		—	%	$	248.9
Municipal bonds		889.3		97.7			20.6		2.3			0.4		—			910.3
Foreign government bonds		216.8		96.9			6.0		2.7			0.8		0.4			223.6
Governmental agency bonds		235.7		100.0			—		—			—		—			235.7
Governmental agency mortgage- backed securities		5,090.6		100.0			—		—			—		—			5,090.6
U.S. corporate debt securities		579.7		55.2			315.2		30.0			155.3		14.8			1,050.2
Foreign corporate debt securities		279.5		57.1			183.6		37.6			25.8		5.3			488.9
	$	7,540.5		91.4	%	$	525.4		6.4	%	$	182.3		2.2	%	$	8,248.2

Included in debt securities at September 30, 2025 were bank loans totaling $121.6 million, of which $113.6 million were non-investment grade; high yield corporate debt securities totaling $65.4 million, all of which were non-investment grade; and emerging market debt securities totaling $30.4 million, of which $2.9 million were non-investment grade.

The composition of the debt securities portfolio in an unrealized loss position at September 30, 2025, by credit rating, is as follows:


	A- or higher					BBB+ to BBB-					Non-Investment Grade					Total
(dollars in millions)	Estimated fair value		Percentage			Estimated fair value		Percentage			Estimated fair value		Percentage			Estimated fair value
U.S. Treasury bonds	$	115.4		100.0	%	$	—		—	%	$	—		—	%	$	115.4
Municipal bonds		551.2		97.3			14.9		2.6			0.3		0.1			566.4
Foreign government bonds		70.1		97.5			1.3		1.8			0.5		0.7			71.9
Governmental agency bonds		174.1		100.0			—		—			—		—			174.1
Governmental agency mortgage- backed securities		3,399.5		100.0			—		—			—		—			3,399.5
U.S. corporate debt securities		144.2		57.2			70.7		28.0			37.3		14.8			252.2
Foreign corporate debt securities		68.1		58.6			41.5		35.7			6.6		5.7			116.2
	$	4,522.6		96.3	%	$	128.4		2.7	%	$	44.7		1.0	%	$	4,695.7

Debt securities in an unrealized loss position at September 30, 2025 included bank loans totaling $32.7 million, of which $32.5 million were non-investment grade; high yield corporate debt securities totaling $11.3 million, all of which were non-investment grade; and emerging market debt securities totaling $11.6 million, of which $0.6 million were non-investment grade.

The credit ratings in the above tables reflect published ratings obtained from globally recognized securities rating agencies. If a security was rated differently among the rating agencies the lowest rating was selected. Governmental agency mortgage-backed securities are not rated by any of the ratings agencies; however, these securities have been included in the above table in the “A- or higher” rating category because the payments of principal and interest are guaranteed by the governmental agency that issued the security.