The Company's investments in marketable debt securities are classified as available-for-sale. These investments are stated at fair value and may include an allowance for credit losses. Changes in the allowance for credit losses are recognized in the current period earnings and any unrealized gains or losses, net of tax, are included as a component of accumulated other comprehensive income (loss) (AOCI).

The Company utilizes third-party pricing services for all of its marketable debt security valuations. The Company reviews the pricing methodology used by the third‑party pricing services, including the manner employed to collect market information. On a quarterly basis, the Company also performs review and validation procedures on the pricing information received from the third‑party providers. These procedures help ensure the fair value information used by the Company is determined in accordance with applicable accounting guidance.

The Company evaluates its investment in marketable debt securities at the end of each reporting period to determine if a decline in fair value is the result of credit losses or unrealized losses. In assessing credit losses, the Company considers the collectability of principal and interest payments by monitoring changes to issuers’ credit ratings, specific credit events associated with individual issuers as well as the credit ratings of any financial guarantor. The Company considers its intent for selling the security and whether it is more likely than not the Company will be able to hold the security until the recovery of any credit losses and unrealized losses. Charges against the allowance for credit losses occur when a security with credit losses is sold or the Company no longer intends to hold that security.

Marketable equity securities are traded on active exchanges and are measured at fair value. The realized and unrealized gains (losses) are recognized in investment income.

Marketable securities at September 30, 2023 and December 31, 2022 consisted of the following:


			UNREALIZED		UNREALIZED		FAIR
At September 30, 2023	COST		GAINS		LOSSES		VALUE
Marketable debt securities
U.S. tax-exempt securities	$	293.0			$	8.1	$	284.9
U.S. taxable municipal / non-U.S. provincial bonds		249.3				9.0		240.3
U.S. corporate securities		354.4				10.2		344.2
U.S. government and agency securities		151.6				4.4		147.2
Non-U.S. corporate securities		510.4				14.3		496.1
Non-U.S. government securities		134.2	$	.2		2.2		132.2
Other debt securities		100.1				4.3		95.8
Marketable equity securities		10.0				7.6		2.4
Total marketable securities	$	1,803.0	$	.2	$	60.1	$	1,743.1


			UNREALIZED		UNREALIZED		FAIR
At December 31, 2022	COST		GAINS		LOSSES		VALUE
Marketable debt securities
U.S. tax-exempt securities	$	452.8	$	.5	$	8.2	$	445.1
U.S. taxable municipal / non-U.S. provincial bonds		191.6				10.8		180.8
U.S. corporate securities		262.5		.1		11.6		251.0
U.S. government and agency securities		118.0		.1		3.1		115.0
Non-U.S. corporate securities		467.9				17.9		450.0
Non-U.S. government securities		78.9		.2		2.7		76.4
Other debt securities		99.4				4.7		94.7
Marketable equity securities		10.0				8.8		1.2
Total marketable securities	$	1,681.1	$	.9	$	67.8	$	1,614.2

The cost of marketable debt securities is adjusted for amortization of premiums and accretion of discounts to maturity. Amortization, accretion, interest and dividend income and realized gains and losses are included in investment income. The cost of securities sold is based on the specific identification method. Gross realized gains were $.9 and $.5 and gross realized losses were $3.6 and $1.5 for the nine months periods ended September 30, 2023 and 2022, respectively.

Net realized gains on marketable equity securities were $1.1 and nil for the nine months periods ending September 30, 2023 and 2022, respectively.

The unrealized losses on marketable debt securities above were due to higher yields on certain securities. The Company did not identify any indicators of a credit loss in its assessments. Accordingly, no allowance for credit losses was recorded at September 30, 2023 and December 31, 2022. The Company does not currently intend, and it is more likely than not that it will not be required to sell the investment securities before recovery of the unrealized losses. The Company expects that the contractual principal and interest will be received on the investment securities.