Investments (Tables)

12 Months Ended

Dec. 31, 2011

Investments [Abstract]

Available for sale securities

The following is a summary of the Company's available-for-sale securities as of December 31, 2011:

(in millions)	Amortized cost		Gross unrealized gains		Gross  unrealized  losses			Fair value (net carrying  amount)
Agency Bonds	$	97.7	$	-	$	(0.1	)	$	97.6
Corporate Bonds		51.7		-		-			51.7
Commercial Paper		19.5		-		-			19.5
U.S. Treasury Bills		0.8		-		-			0.8
Total available-for-sale securities	$	169.7	$	-	$	(0.1	)	$	169.6

The following is a summary of the Company's available-for-sale securities as of December 31, 2010:

(in millions)	Amortized cost		Gross unrealized  gains		Gross  unrealized  losses			Fair value  (net carrying  amount)
Corporate Bonds	$	44.5	$	-	$	(0.1	)	$	44.4
Agency Bonds		31.0		-		-			31.0
Commercial Paper		29.5		-		-			29.5
U.S. Treasury Bills		0.8		-		-			0.8
Total available-for-sale securities	$	105.8	$	-	$	(0.1	)	$	105.7

The net carrying value and estimated fair value of debt securities at December 31, 2011, by contractual maturity, are shown below:

(in millions)	Amortized  cost		Fair value  (net carrying  amount)
Available-for-sale debt securities:
Due in one year or less	$	76.7	$	76.7
Due after one year through two years		93.0		92.9
Total available-for-sale debt securities	$	169.7	$	169.6

The net carrying value and estimated fair value of debt securities at December 31, 2010, by contractual maturity, are shown below:

(in millions)	Amortized  cost		Fair value  (net carrying amount)
Available-for-sale debt securities:
Due in one year or less	$	84.8	$	84.7
Due after one year through two years		21.0		21.0
Total available-for-sale debt securities	$	105.8	$	105.7