Investments in Marketable Securities (Tables)

3 Months Ended

Mar. 31, 2025

Investments, Debt and Equity Securities [Abstract]

Marketable Securities

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

			UNREALIZED		UNREALIZED		FAIR
At March 31, 2025	COST		GAINS		LOSSES		VALUE
Marketable debt securities
U.S. tax-exempt securities	$	296.6	$	.7	$	.5	$	296.8
U.S. taxable municipal / non-U.S. provincial bonds		400.5		2.7		1.0		402.2
U.S. corporate securities		904.0		6.1		1.5		908.6
U.S. government securities		241.7		1.1		.4		242.4
Non-U.S. corporate securities		605.5		4.6		.9		609.2
Non-U.S. government securities		178.0		1.7		.3		179.4
Other debt securities		180.6		1.2		.6		181.2
Marketable equity securities		10.0				3.3		6.7
Total marketable securities	$	2,816.9	$	18.1	$	8.5	$	2,826.5

			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:

	March 31, 2025				December 31, 2024
	LESS THAN		TWELVE MONTHS		LESS THAN		TWELVE MONTHS
	TWELVE MONTHS		OR GREATER		TWELVE MONTHS		OR GREATER
Fair value	$	533.3	$	264.7	$	932.9	$	365.5
Unrealized losses		1.6		3.6		5.5		6.2

Contractual Maturities on Debt Securities

Contractual maturities on marketable debt securities at March 31, 2025 were as follows:

	AMORTIZED		FAIR
	COST		VALUE
Within one year	$	525.9	$	526.0
One to five years		2,275.0		2,288.3
Six to ten years		1.0		1.0
More than ten years		5.0		4.5
	$	2,806.9	$	2,819.8