Investments (Tables)

12 Months Ended

Dec. 31, 2014

Investments, Debt and Equity Securities [Abstract]

Investments in Short and Long-Term Classified as Available-for-Sale Securities

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

			Gross Unrealized					Fair value
	Amortized Cost		Gains		Losses
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
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

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, 2014	Amortized Cost		Fair Value
Due in one year or less	$	612.6	$	612.5
Due after one year through two years		256.7		256.4
Total	$	869.3	$	868.9