Investments in Marketable Securities (Tables)

9 Months Ended

Sep. 30, 2025

Investments, Debt and Equity Securities [Abstract]

Marketable Securities

Marketable securities at September 30, 2025 and December 31, 2024 consisted of the following:

			UNREALIZED		UNREALIZED		FAIR
At September 30, 2025	COST		GAINS		LOSSES		VALUE
Marketable debt securities
U.S. tax-exempt securities	$	331.2	$	4.8	$	.1	$	335.9
U.S. taxable municipal / non-U.S. provincial bonds		389.4		4.2		.3		393.3
U.S. corporate securities		909.4		8.7		.4		917.7
U.S. government securities		299.4		2.0		.2		301.2
Non-U.S. corporate securities		596.0		5.9		.3		601.6
Non-U.S. government securities		203.1		1.2		.2		204.1
Other debt securities		185.9		1.6		.2		187.3
Marketable equity securities		10.0				4.6		5.4
Total marketable securities	$	2,924.4	$	28.4	$	6.3	$	2,946.5

			UNREALIZED		UNREALIZED		FAIR
At December 31, 2024	COST		GAINS		LOSSES		VALUE
Marketable debt securities
U.S. tax-exempt securities	$	304.5	$	.6	$	1.4	$	303.7
U.S. taxable municipal / non-U.S. provincial bonds		381.1		1.2		2.2		380.1
U.S. corporate securities		864.3		3.1		3.2		864.2
U.S. government securities		287.1		.1		1.5		285.7
Non-U.S. corporate securities		606.6		3.5		2.0		608.1
Non-U.S. government securities		163.5		1.4		.6		164.3
Other debt securities		166.4		.8		.8		166.4
Marketable equity securities		10.0				3.7		6.3
Total marketable securities	$	2,783.5	$	10.7	$	15.4	$	2,778.8

Marketable Debt Securities Continuous Unrealized Losses

Marketable debt securities with continuous unrealized losses and their related fair values were as follows:

	September 30, 2025				December 31, 2024
	LESS THAN		TWELVE MONTHS		LESS THAN		TWELVE MONTHS
	TWELVE MONTHS		OR GREATER		TWELVE MONTHS		OR GREATER
Fair value	$	154.2	$	123.1	$	932.9	$	365.5
Unrealized losses		.3		1.4		5.5		6.2

Contractual Maturities of Debt Securities

Contractual maturities of marketable debt securities at September 30, 2025 were as follows:

	AMORTIZED		FAIR
	COST		VALUE
Within one year	$	549.0	$	550.6
One to five years		2,362.0		2,387.3
Six to ten years		.8		.8
More than ten years		2.6		2.4
	$	2,914.4	$	2,941.1