Investments (Tables)

12 Months Ended

Dec. 31, 2015

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
	Amortized Cost		Gains		Losses			Fair value
As of December 31, 2015
Corporate debt securities	$	245.7	$	0.1	$	(0.4	)	$	245.4
U.S. government and agency debt securities		21.6		–		(0.1	)		21.5
Commercial paper		4.2		–		–			4.2
Certificates of deposit		2.0		–		–			2.0
Total short and long-term investments	$	273.5	$	0.1	$	(0.5	)	$	273.1
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

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, 2015	Amortized Cost		Fair Value
Due in one year or less	$	164.7	$	164.6
Due after one year through two years		108.8		108.5
Total	$	273.5	$	273.1