Investments in Marketable Securities (Tables)

12 Months Ended

Dec. 31, 2021

Investments Debt And Equity Securities [Abstract]

Marketable Securities

Marketable securities consisted of the following at December 31:

			UNREALIZED		UNREALIZED		FAIR
2021	COST		GAINS		LOSSES		VALUE
Marketable debt securities
U.S. tax-exempt securities	$	431.4	$	1.5	$	.4	$	432.5
U.S. corporate securities		208.3		.6		1.5		207.4
U.S. government and agency securities		95.9		.6		.1		96.4
Non-U.S. corporate securities		443.9		1.4		2.5		442.8
Non-U.S. government securities		75.2		.1		.3		75.0
Other debt securities		292.6		.9		1.9		291.6
Marketable equity securities		15.4		1.3		3.0		13.7
Total marketable securities	$	1,562.7	$	6.4	$	9.7	$	1,559.4

			UNREALIZED		UNREALIZED		FAIR
2020	COST		GAINS		LOSSES		VALUE
U.S. tax-exempt securities	$	388.1	$	4.4	$	.1	$	392.4
U.S. corporate securities		229.6		3.3				232.9
U.S. government and agency securities		92.1		2.3				94.4
Non-U.S. corporate securities		406.0		5.5				411.5
Non-U.S. government securities		77.0		.5				77.5
Other debt securities		216.9		3.4				220.3
Total marketable securities	$	1,409.7	$	19.4	$	.1	$	1,429.0

Marketable Debt Securities Continuous Unrealized Losses

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

At December 31,	2021				2020
	LESS THAN TWELVE MONTHS		TWELVE MONTHS OR GREATER		LESS THAN TWELVE MONTHS		TWELVE MONTHS OR GREATER
Fair value	$	911.2	$	1.3	$	81.1	$	1.3
Unrealized losses		6.7				.1

Contractual Maturities of Debt Securities

Contractual maturities on marketable debt securities at December 31, 2021 were as follows:

	AMORTIZED		FAIR
Maturities:	COST		VALUE
Within one year	$	424.3	$	425.6
One to five years		1,099.7		1,097.1
Six to ten years		9.8		9.7
More than ten years		13.5		13.3
	$	1,547.3	$	1,545.7