INVESTMENTS

Investments classified as available-for-sale, which consist primarily of debt securities, are stated at fair value. Unrealized gains and losses are excluded from earnings and reported as other comprehensive income, net of income tax effects. The cost of investments sold is determined in accordance with the specific identification method, and realized gains and losses are included in net investment income. We periodically assess our available-for-sale investments for other-than-temporary impairment. Any such other-than-temporary impairment loss is recognized as a realized loss, which is recorded through earnings, if related to credit losses.

During the three months ended March 31, 2013 and 2012, we recognized no losses from other-than-temporary impairments of our cash equivalents and available-for-sale investments.

We had no noncurrent available-for-sale investments as of March 31, 2013 and December 31, 2012.

As of March 31, 2013 and December 31, 2012, the amortized cost, gross unrealized holding gains and losses, and fair value of our current investments available-for-sale, after giving effect to other-than-temporary impairments, were as follows:



	March 31, 2013
	Amortized Cost		Gross Unrealized Holding Gains		Gross Unrealized Holding Losses			Carrying Value
	(Dollars in millions)
Current:
Asset-backed securities	$	430.1	$	9.9	$	(0.7	)	$	439.3
U.S. government and agencies	26.4		—		—			26.4
Obligations of states and other political subdivisions	847.3		18.6		(5.1		)	860.8
Corporate debt securities	431.2		10.3		(0.8		)	440.7
	$	1,735.0	$	38.8	$	(6.6	)	$	1,767.2



	December 31, 2012
	Amortized Cost		Gross Unrealized Holding Gains		Gross Unrealized Holding Losses			Carrying Value
	(Dollars in millions)
Current:
Asset-backed securities	$	499.7	$	19.6	$	(0.2	)	$	519.1
U.S. government and agencies	25.9		—		—			25.9
Obligations of states and other political subdivisions	819.9		24.2		(2.0		)	842.1
Corporate debt securities	408.4		17.5		(0.5		)	425.4
	$	1,753.9	$	61.3	$	(2.7	)	$	1,812.5

As of March 31, 2013, the contractual maturities of our current investments available-for-sale were as follows:



	Amortized Cost		Estimated Fair Value
Current:	(Dollars in millions)
Due in one year or less	$	34.4	$	34.4
Due after one year through five years	234.3		240.7
Due after five years through ten years	505.0		517.9
Due after ten years	531.2		534.9
Asset-backed securities	430.1		439.3
Total current investments available-for-sale	$	1,735.0	$	1,767.2

Proceeds from sales of investments available-for-sale during the three months ended March 31, 2013 were $354.8 million. Gross realized gains and losses totaled $17.5 million and $0.2 million, respectively, for the three months ended March 31, 2013. Proceeds from sales of investments available-for-sale during the three months ended March 31, 2012 were $650.8 million. Gross realized gains and losses totaled $13.4 million and $0.4 million, respectively, for the three months ended March 31, 2012.

The following tables show our investments’ fair values and gross unrealized losses for individual securities that have been in a continuous loss position through March 31, 2013 and December 31, 2012. These investments are interest-yielding debt securities of varying maturities. We have determined that the unrealized loss position for these securities is primarily due to market volatility. Generally, in a rising interest rate environment, the estimated fair value of fixed income securities would be expected to decrease; conversely, in a decreasing interest rate environment, the estimated fair value of fixed income securities would be expected to increase. These securities may also be negatively impacted by illiquidity in the market.

The following table shows our current investments' fair values and gross unrealized losses for individual securities that have been in a continuous loss position through March 31, 2013:



	Less than 12 Months					12 Months or More				Total
	Fair Value		Unrealized Losses			Fair Value		Unrealized Losses		Fair Value		Unrealized Losses
	(Dollars in millions)
Asset-backed securities	$	122.2	$	(0.7	)	$	0.7	$	—	$	122.9	$	(0.7	)
U.S. government and agencies	8.0		—			—		—		8.0		—
Obligations of states and other political subdivisions	321.6		(5.1		)	0.2		—		321.8		(5.1		)
Corporate debt securities	72.1		(0.8		)	1.4		—		73.5		(0.8		)
	$	523.9	$	(6.6	)	$	2.3	$	—	$	526.2	$	(6.6	)

The following table shows the number of our individual securities-current that have been in a continuous loss position through March 31, 2013:



	Less than 12 Months	12 Months or More	Total
Asset-backed securities	44	4	48
U.S. government and agencies	1	—	1
Obligations of states and other political subdivisions	137	1	138
Corporate debt securities	61	1	62
	243	6	249

The following table shows our current investments’ fair values and gross unrealized losses for individual securities that have been in a continuous loss position through December 31, 2012:



	Less than 12 Months					12 Months or More				Total
	Fair Value		Unrealized Losses			Fair Value		Unrealized Losses		Fair Value		Unrealized Losses
	(Dollars in millions)
Asset-backed securities	$	54.9	$	(0.2	)	$	0.1	$	—	$	55.0	$	(0.2	)
U.S. government and agencies	10.1		—			—		—		10.1		—
Obligations of states and other political subdivisions	192.1		(2.0		)	0.2		—		192.3		(2.0		)
Corporate debt securities	45.9		(0.5		)	—		—		45.9		(0.5		)
	$	303.0	$	(2.7	)	$	0.3	$	—	$	303.3	$	(2.7	)