Investments (Tables)

12 Months Ended

Dec. 31, 2011

Investments [Abstract]

Investments in short and long-term classified as available-for-sale securities

	Amortized Cost		Gross Unrealized					Fair value
			Gains		Losses
As of December 31, 2011
Corporate debt securities	$	324.8	$	0.2	$	(0.3	)	$	324.7
U.S. government and agency debt securities		177.1		0.1		–			177.2
Municipal bonds		1.0		–		–			1.0
Foreign government debt securities		6.8		–		–			6.8
Commercial paper		74.5		–		–			74.5
Certificates of deposit		88.5		–		–			88.5
Total short and long-term investments	$	672.7	$	0.3	$	(0.3	)	$	672.7
As of December 31, 2010
Corporate debt securities	$	203.9	$	0.1	$	(0.2	)	$	203.8
U.S. government and agency debt securities		47.9		–		–			47.9
Municipal bonds		1.1		–		–			1.1
Foreign government debt securities		10.3		–		–			10.3
Commercial paper		16.1		–		–			16.1
Certificates of deposit		131.5		–		(0.1	)		131.4
Total short and long-term investments	$	410.8	$	0.1	$	(0.3	)	$	410.6

Fair values and gross unrealized losses for all available-for-sale securities in an unrealized loss position deemed to be temporary

The following table shows the fair value and gross unrealized losses for all available-for-sale securities in an unrealized loss position deemed to be temporary (in millions):

	As of December 31, 2011					As of December 31, 2010
	Fair Value		Unrealized Losses			Fair value		Unrealized Losses
Corporate debt securities	$	164.5	$	(0.3	)	$	126.1	$	(0.2	)
Certificates of deposit		–		–			50.6		(0.1	)
Total	$	164.5	$	(0.3	)	$	176.7	$	(0.3	)

The cost and fair value of available-for-sale fixed-maturity securities by contractual maturity

The amortized cost and fair value of our available-for-sale fixed-maturity securities by contractual maturity are as follows (in millions):

As of December 31, 2011	Amortized Cost		Fair Value
Due in one year or less	$	455.4	$	455.5
Due after one year through two years		217.3		217.2
Total	$	672.7	$	672.7