Investments in Marketable Debt Securities (Tables)

12 Months Ended

Dec. 31, 2019

Available For Sale Securities [Abstract]

Marketable Debt Securities

Marketable debt securities consisted of the following at December 31:

	AMORTIZED		UNREALIZED		UNREALIZED		FAIR
2019	COST		GAINS		LOSSES		VALUE
U.S. tax-exempt securities	$	318.1	$	2.2	$	.1	$	320.2
U.S. corporate securities		163.8		1.9				165.7
U.S. government and agency securities		128.4		.9				129.3
Non-U.S. corporate securities		347.7		2.3		.2		349.8
Non-U.S. government securities		72.3		.2		.1		72.4
Other debt securities		123.7		1.1		.1		124.7
	$	1,154.0	$	8.6	$	.5	$	1,162.1

	AMORTIZED		UNREALIZED		UNREALIZED		FAIR
2018	COST		GAINS		LOSSES		VALUE
U.S. tax-exempt securities	$	326.0	$	.3	$	1.2	$	325.1
U.S. corporate securities		147.6		.2		.4		147.4
U.S. government and agency securities		98.9		.2		.4		98.7
Non-U.S. corporate securities		272.5		.4		1.6		271.3
Non-U.S. government securities		55.9		.1		.1		55.9
Other debt securities		122.6		.2		.8		122.0
	$	1,023.5	$	1.4	$	4.5	$	1,020.4

Marketable Debt Securities Continuous Unrealized Losses

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

At December 31,	2019				2018
	LESS THAN TWELVE MONTHS		TWELVE MONTHS OR GREATER		LESS THAN TWELVE MONTHS		TWELVE MONTHS OR GREATER
Fair value	$	177.0	$	31.4	$	252.8	$	397.9
Unrealized losses		.4		.1		.8		3.7

Contractual Maturities of Debt Securities

Contractual maturities on marketable debt securities at December 31, 2019 were as follows:

	AMORTIZED		FAIR
Maturities:	COST		VALUE
Within one year	$	291.6	$	292.1
One to five years		806.4		813.9
Six to ten years		24.0		24.1
More than ten years		32.0		32.0
	$	1,154.0	$	1,162.1