Investments

9 Months Ended

Sep. 30, 2015

Investments, Debt and Equity Securities [Abstract]

Investments

7. 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 September 30, 2015
Corporate debt securities	$	372.1	$	0.3	$	(0.2	)	$	372.2
U.S. government and agency debt securities		66.9		—		—			66.9
Commercial paper		11.5		—		—			11.5
Certificates of deposit		15.9		—		—			15.9
Total short and long-term investments	$	466.4	$	0.3	$	(0.2	)	$	466.5
As of December 31, 2014
Corporate debt securities	$	516.9	$	0.1	$	(0.5	)	$	516.5
U.S. government and agency debt securities		194.3		—		—			194.3
Commercial paper		57.8		—		—			57.8
Certificates of deposit		100.3		—		—			100.3
Total short and long-term investments	$	869.3	$	0.1	$	(0.5	)	$	868.9

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 September 30, 2015 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):

	September 30, 2015
	Amortized Cost		Fair Value
Due in one year or less	$	343.2	$	343.3
Due after one year through two years		123.2		123.2
Total	$	466.4	$	466.5