Investments (Tables)

3 Months Ended

Mar. 31, 2013

Fair Value of Investments Available-for-Sale

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

Available-for-Sale Current Investments Classified by Contractual Maturity Date

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

Schedule of Unrealized Loss on Investments

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 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	)

Number of Securities Included in Loss Position of Current Investments

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