Investments in Marketable Debt Securities

12 Months Ended

Dec. 31, 2016

Investments, Debt and Equity Securities [Abstract]

Investments in Marketable Debt Securities

B. INVESTMENTS IN MARKETABLE DEBT SECURITIES

Marketable debt securities consisted of the following at December 31:

2016	AMORTIZED COST		UNREALIZED GAINS		UNREALIZED LOSSES		FAIR VALUE
U.S. tax-exempt securities	$	597.9	$	.2	$	3.1	$	595.0
U.S. corporate securities		47.6		.2				47.8
U.S. government and agency securities		16.0						16.0
Non-U.S. corporate securities		306.9		1.5		.4		308.0
Non-U.S. government securities		97.6		.6				98.2
Other debt securities		75.9		.2		.2		75.9
	$	1,141.9	$	2.7	$	3.7	$	1,140.9
2015	AMORTIZED COST		UNREALIZED GAINS		UNREALIZED LOSSES		FAIR VALUE
U.S. tax-exempt securities	$	505.0	$	.7	$	.3	$	505.4
U.S. corporate securities		76.7		.1		.1		76.7
U.S. government and agency securities		15.7		.1		.1		15.7
Non-U.S. corporate securities		585.6		1.8		.4		587.0
Non-U.S. government securities		192.7		1.1		.1		193.7
Other debt securities		69.6		.1		.1		69.6
	$	1,445.3	$	3.9	$	1.1	$	1,448.1

The cost of marketable debt securities is adjusted for amortization of premiums and accretion of discounts to maturity. Amortization, accretion, interest and dividend income and realized gains and losses are included in investment income. The cost of securities sold is based on the specific identification method. Gross realized gains were $4.4, $2.6 and $1.2, and gross realized losses were $.1, $.8 and $.1 for the years ended December 31, 2016, 2015 and 2014, respectively.

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

At December 31,	2016			2015
	LESS THAN TWELVE MONTHS		TWELVE MONTHS OR GREATER	LESS THAN TWELVE MONTHS		TWELVE MONTHS OR GREATER
Fair value	$	615.5		$	579.0
Unrealized losses		3.7			1.1

For the investment securities in gross unrealized loss positions identified above, the Company does not intend to sell the investment securities. It is more likely than not that the Company will not be required to sell the investment securities before recovery of the unrealized losses, and the Company expects that the contractual principal and interest will be received on the investment securities. As a result, the Company recognized no other-than-temporary impairments during the periods presented.

Contractual maturities on marketable debt securities at December 31, 2016 were as follows:

Maturities:	AMORTIZED COST		FAIR             VALUE
Within one year	$	274.5	$	274.7
One to five years		858.2		857.0
Six to ten years		.1		.1
More than ten years		9.1		9.1
	$	1,141.9	$	1,140.9