Investments in Marketable Securities (Tables)

9 Months Ended

Sep. 30, 2024

Investments, Debt and Equity Securities [Abstract]

Marketable Securities

Marketable securities at September 30, 2024 and December 31, 2023 consisted of the following:

			UNREALIZED		UNREALIZED		FAIR
At September 30, 2024	COST		GAINS		LOSSES		VALUE
Marketable debt securities
U.S. tax-exempt securities	$	303.9	$	2.3	$	.7	$	305.5
U.S. taxable municipal / non-U.S. provincial bonds		321.5		3.0		2.3		322.2
U.S. corporate securities		744.5		9.3		1.8		752.0
U.S. government securities		214.1		1.5		.3		215.3
Non-U.S. corporate securities		617.8		6.1		2.1		621.8
Non-U.S. government securities		168.5		2.2		.5		170.2
Other debt securities		117.2		1.3		.7		117.8
Marketable equity securities		10.0				4.1		5.9
Total marketable securities	$	2,497.5	$	25.7	$	12.5	$	2,510.7

			UNREALIZED		UNREALIZED		FAIR
At December 31, 2023	COST		GAINS		LOSSES		VALUE
Marketable debt securities
U.S. tax-exempt securities	$	312.5	$	1.2	$	3.0	$	310.7
U.S. taxable municipal / non-U.S. provincial bonds		244.9		.8		5.6		240.1
U.S. corporate securities		357.1		1.4		5.2		353.3
U.S. government securities		159.2		.6		1.7		158.1
Non-U.S. corporate securities		529.4		2.3		7.5		524.2
Non-U.S. government securities		141.0		1.5		1.3		141.2
Other debt securities		92.8		.3		2.5		90.6
Marketable equity securities		10.0				5.6		4.4
Total marketable securities	$	1,846.9	$	8.1	$	32.4	$	1,822.6

Marketable Debt Securities Continuous Unrealized Losses

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

	September 30, 2024				December 31, 2023
	LESS THAN		TWELVE MONTHS		LESS THAN		TWELVE MONTHS
	TWELVE MONTHS		OR GREATER		TWELVE MONTHS		OR GREATER
Fair value	$	108.6	$	489.5	$	289.0	$	798.5
Unrealized losses		.1		8.3		1.6		25.2

Contractual Maturities of Debt Securities

Contractual maturities of marketable debt securities at September 30, 2024 were as follows:

	AMORTIZED		FAIR
	COST		VALUE
Within one year	$	619.1	$	617.7
One to five years		1,859.0		1,878.2
Six to ten years
More than ten years		9.4		8.9
	$	2,487.5	$	2,504.8