Financial Instruments

On April 2, 2013, we used $3.25 billion to fund the upfront payment in connection with our acquisition of the TYSABRI rights.

Marketable Securities

The following tables summarize our marketable debt and equity securities:



As of December 31, 2013 (In millions)	Fair Value		Gross Unrealized Gains		Gross Unrealized Losses			Amortized Cost
Available-for-sale:
Corporate debt securities
Current	$	100.7	$	—	$	—		$	100.7
Non-current	339.1		0.4		(0.1		)	338.8
Government securities
Current	519.5		—		—			519.5
Non-current	155.2		—		(0.1		)	155.3
Mortgage and other asset backed securities
Current	—		—		—			—
Non-current	131.4		—		(0.1		)	131.5
Total marketable debt securities	$	1,245.9	$	0.4	$	(0.3	)	$	1,245.8
Marketable equity securities, non-current	$	11.2	$	8.7	$	—		$	2.5



As of December 31, 2012 (In millions)	Fair Value		Gross Unrealized Gains		Gross Unrealized Losses			Amortized Cost
Available-for-sale:
Corporate debt securities
Current	$	346.9	$	0.3	$	—		$	346.6
Non-current	654.1		2.8		(0.6		)	651.9
Government securities
Current	783.4		0.3		—			783.1
Non-current	874.4		0.8		—			873.6
Mortgage and other asset backed securities
Current	4.8		—		—			4.8
Non-current	508.1		1.4		(1.3		)	508.0
Total marketable debt securities	$	3,171.7	$	5.6	$	(1.9	)	$	3,168.0
Marketable equity securities, non-current	$	9.0	$	3.0	$	—		$	6.0

The following table summarizes our financial assets with maturities of less than 90 days from the date of purchase included within cash and cash equivalents on the accompanying consolidated balance sheet:



	As of December 31,
(In millions)	2013		2012
Commercial paper	$	1.2	$	40.7
Overnight reverse repurchase agreements	22.4		67.4
Short-term debt securities	401.1		331.3
Total	$	424.7	$	439.4

The carrying values of our commercial paper, including accrued interest, overnight reverse repurchase agreements, and our short-term debt securities approximate fair value due to their short term maturities.

Summary of Contractual Maturities: Available-for-Sale Securities

The estimated fair value and amortized cost of our marketable debt securities available-for-sale by contractual maturity are summarized as follows:



	As of December 31, 2013				As of December 31, 2012
(In millions)	Estimated Fair Value		Amortized Cost		Estimated Fair Value		Amortized Cost
Due in one year or less	$	620.2	$	620.2	$	1,135.0	$	1,134.5
Due after one year through five years	573.1		572.9		1,744.3		1,741.2
Due after five years	52.6		52.7		292.4		292.3
Total available-for-sale securities	$	1,245.9	$	1,245.8	$	3,171.7	$	3,168.0

The average maturity of our marketable debt securities available-for-sale as of December 31, 2013 and 2012, was 13 months and 14 months, respectively.

Proceeds from Marketable Debt Securities

The proceeds from maturities and sales of marketable debt securities and resulting realized gains and losses are summarized as follows:



	For the Years Ended December 31,
(In millions)	2013		2012		2011
Proceeds from maturities and sales	$	5,190.1	$	2,749.6	$	2,276.7
Realized gains	$	6.6	$	2.1	$	3.9
Realized losses	$	2.1	$	3.5	$	2.3

Realized losses for the year ended December 31, 2013, primarily relate to sales of agency mortgage-backed securities and corporate securities. Realized losses for the year ended December 31, 2012, primarily relate to sales of agency mortgage-backed securities. Realized losses for the year ended December 31, 2011, primarily relate to the sale of government and corporate securities.

Strategic Investments

As of December 31, 2013 and 2012, our strategic investment portfolio was comprised of investments totaling $56.9 million and $64.2 million, respectively, which are included in investments and other assets in our accompanying consolidated balance sheets.

Our strategic investment portfolio includes investments in marketable equity securities of certain biotechnology companies and our investments in venture capital funds accounted for at fair value which totaled $33.1 million and $29.3 million as of December 31, 2013 and 2012, respectively. Our strategic investment portfolio also includes other equity investments in privately-held companies and additional investments in venture capital funds accounted for under the cost method. The carrying value of these investments totaled $23.8 million and $34.9 million, as of December 31, 2013 and 2012, respectively.

Changes in Fair Value

During the years ended December 31, 2013, 2012, and 2011, we realized changes in fair value recorded through income of $14.4 million, $6.5 million and $7.3 million, respectively, on our strategic investment portfolio. In 2013, we sold our stock in Portola for a gain of $7.1 million. Included within changes in fair value recognized during the year ended December 31, 2012, was a gain of $9.0 million recognized upon our acquisition of Stromedix as we previously held an equity interest. For a more detailed description of this transaction, please read Note 2, Acquisitions to these consolidated financial statements. In 2011 we sold four strategic investments for $40.6 million, which resulted in a net gain of $13.5 million.

Impairments

During the years ended December 31, 2013, 2012, and 2011, we recognized impairment charges on our marketable equity securities of certain biotechnology companies, investments in venture capital funds accounted for under the cost method and investments in privately-held companies totaling $2.8 million, $5.5 million, and $9.9 million, respectively.