Financial Instruments

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

Marketable Securities

The following tables summarize our marketable debt and equity securities:



As of June 30, 2013 (In millions)	Fair Value		Gross Unrealized Gains		Gross Unrealized Losses			Amortized Cost
Available-for-sale:
Corporate debt securities
Current	$	26.4	$	—	$	—		$	26.4
Non-current	73.2		—		(0.2		)	73.4
Government securities
Current	248.8		—		—			248.8
Non-current	24.4		—		—			24.4
Mortgage and other asset backed securities
Current	—		—		—			—
Non-current	9.5		—		—			9.5
Total marketable debt securities	$	382.3	$	—	$	(0.2	)	$	382.5
Marketable equity securities, non-current	$	28.9	$	14.7	$	—		$	14.2



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 condensed consolidated balance sheet:



(In millions)	As of June 30, 2013		As of December 31, 2012
Commercial paper	$	10.3	$	40.7
Overnight repurchase agreements	—		67.4
Short-term debt securities	251.2		331.3
Total	$	261.5	$	439.4

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

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 June 30, 2013				As of December 31, 2012
(In millions)	Estimated Fair Value		Amortized Cost		Estimated Fair Value		Amortized Cost
Due in one year or less	$	275.2	$	275.3	$	1,135.0	$	1,134.5
Due after one year through five years	103.9		104.0		1,744.3		1,741.2
Due after five years	3.2		3.2		292.4		292.3
Total available-for-sale securities	$	382.3	$	382.5	$	3,171.7	$	3,168.0

The average maturity of our marketable debt securities available-for-sale as of June 30, 2013 and December 31, 2012 was 11 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 Three Months Ended June 30,					For the Six Months Ended June 30,
(In millions)	2013		2012			2013			2012
Proceeds from maturities and sales	$	78.3	$	599.6		$	4,404.7		$	1,423.9
Realized gains	$	—	$	0.6		$	6.3		$	1.3
Realized losses	$	—	$	(1.3	)	$	(2.0	)	$	(2.0	)

Strategic Investments

As of June 30, 2013 and December 31, 2012, our strategic investment portfolio was comprised of investments totaling $77.6 million and $64.2 million, respectively, which are included in investments and other assets in our accompanying condensed 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 $52.4 million and $29.3 million as of June 30, 2013 and December 31, 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 $25.2 million and $34.9 million as of June 30, 2013 and December 31, 2012, respectively.

Net Gains, Impairments and Changes to Fair Value

During the three and six months ended June 30, 2013, we realized net gains, impairments and changes to fair value recorded through income of $4.4 million and $4.1 million, respectively, on our strategic investment portfolio as compared to $2.2 million and $13.5 million, respectively, in the prior year comparative periods. The net gains recognized during the six months ended June 30, 2012 included 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 our consolidated financial statements included within our 2012 Form 10-K.

Impairments

For the three and six months ended June 30, 2013, 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 $1.4 million and $1.7 million, respectively, as compared to $0.8 million and $1.3 million, respectively, in the prior year comparative periods.