Investments in Marketable Securities (Tables)

6 Months Ended

Jun. 30, 2024

Investments, Debt and Equity Securities [Abstract]

Marketable Securities

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

			UNREALIZED		UNREALIZED		FAIR
At June 30, 2024	COST		GAINS		LOSSES		VALUE
Marketable debt securities
U.S. tax-exempt securities	$	302.6	$	.3	$	2.7	$	300.2
U.S. taxable municipal / non-U.S. provincial bonds		323.2		.2		5.0		318.4
U.S. corporate securities		566.0		.9		4.8		562.1
U.S. government securities		168.5				1.9		166.6
Non-U.S. corporate securities		543.6		1.1		5.0		539.7
Non-U.S. government securities		158.8		.7		1.1		158.4
Other debt securities		98.5		.3		1.5		97.3
Marketable equity securities		10.0				7.2		2.8
Total marketable securities	$	2,171.2	$	3.5	$	29.2	$	2,145.5

			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:

	June 30, 2024				December 31, 2023
	LESS THAN		TWELVE MONTHS		LESS THAN		TWELVE MONTHS
	TWELVE MONTHS		OR GREATER		TWELVE MONTHS		OR GREATER
Fair value	$	683.4	$	704.7	$	289.0	$	798.5
Unrealized losses		3.3		18.7		1.6		25.2

Contractual Maturities of Debt Securities

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

	AMORTIZED		FAIR
	COST		VALUE
Within one year	$	502.5	$	497.2
One to five years		1,646.4		1,634.3
Six to ten years
More than ten years		12.3		11.2
	$	2,161.2	$	2,142.7