Investments (Tables)

12 Months Ended

Dec. 31, 2012

Investments, Debt and Equity Securities [Abstract]

Investments in available-for-sale securities

Investments in available-for-sale securities at December 31, 2012 were as follows:

Available-for-sale securities	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value
	(Dollars in millions)
Current:
U.S. corporate bonds	$	4.1	$	—	$	—	$	4.1
Noncurrent:
Marketable equity securities	32.4		—		—		32.4
Federal government securities	32.0		0.2		—		32.2
U.S. corporate bonds	19.5		0.2		—		19.7
Total	$	88.0	$	0.4	$	—	$	88.4

Investments in available-for-sale securities at December 31, 2011 were as follows:

Available-for-sale securities	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
			(Dollars in millions)
Current:
Federal government securities	$	3.3	$	—	$	—		$	3.3
U.S. corporate bonds	3.9		—		—			3.9
Noncurrent:
Marketable equity securities	67.9		—		(10.9		)	57.0
Federal government securities	11.3		0.2		—			11.5
U.S. corporate bonds	7.7		0.1		—			7.8
Total	$	94.1	$	0.3	$	(10.9	)	$	83.5

Contractual maturities for available for sale investment in debt securities

Contractual maturities for available-for-sale investments in debt securities at December 31, 2012 were as shown below. Expected maturities will differ from contractual maturities because borrowers may have the right to call or prepay obligations with or without call or prepayment penalties.

Contractual maturities for available-for-sale securities	Cost		Fair Value
	(Dollars in millions)
Due in one year or less	$	4.1	$	4.1
Due in one to five years	51.5		51.9
Total	$	55.6	$	56.0