Investments

6 Months Ended

Jun. 30, 2014

Investments Debt And Equity Securities [Abstract]

Investments

5. Investments

We invest in short and long-term investments classified as available-for-sale securities. Information regarding our investments is as follows (in millions):

	Amortized Cost		Gross Unrealized					Fair value
			Gains		Losses
As of June 30, 2014
Corporate debt securities	$	323.6	$	0.3	$	(0.1	)	$	323.8
U.S. government and agency debt securities		185.1		—		—			185.1
Foreign government debt securities		8.1		—		—			8.1
Commercial paper		314.6		—		—			314.6
Certificates of deposit		65.2		—		—			65.2
Total short and long-term investments	$	896.6	$	0.3	$	(0.1	)	$	896.8
As of December 31, 2013
Corporate debt securities	$	457.6	$	0.4	$	(0.1	)	$	457.9
U.S. government and agency debt securities		211.1		0.1		—			211.2
Foreign government debt securities		3.1		—		—			3.1
Commercial paper		68.3		—		—			68.3
Certificates of deposit		67.2		—		—			67.2
Total short and long-term investments	$	807.3	$	0.5	$	(0.1	)	$	807.7

The unrealized losses on our investments in corporate debt securities were caused by increases in interest yields in the global credit markets. We believe the unrealized losses associated with these securities as of June 30, 2014 are temporary because we do not intend to sell these investments, and we do not believe we will be required to sell them before recovery of their amortized cost basis.

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

	June 30, 2014
	Amortized Cost		Fair Value
Due in one year or less	$	729.3	$	729.3
Due after one year through two years		167.3		167.5
Total	$	896.6	$	896.8