Note 3. Investments

Available-for-sale investments, including accrued interest, as of September 30, 2011 and December 31, 2010 were as follows:


	September 30, 2011
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
Corporate debt securities	$	325,872	$	4,638	$	(848	)	$	329,662
Residential mortgage-backed securities		90,422		1,449		(41	)		91,830
Government-sponsored enterprise securities		15,251		62		—			15,313
Asset-backed securities		65,257		81		(6	)		65,332

Subtotal - Marketable securities		496,802		6,230		(895	)		502,137


Restricted cash and cash equivalents		8,844		—		—			8,844
U.S. Treasury and agencies		1,300		5		—			1,305
Corporate debt securities		50,139		337		(192	)		50,284
Residential mortgage-backed securities		7,768		44		(11	)		7,801
Government-sponsored enterprise securities		8,544		18		(2	)		8,560
Asset-backed securities		3,122		5		—			3,127

Subtotal - Restricted investments		79,717		409		(205	)		79,921


Total	$	576,519	$	6,639	$	(1,100	)	$	582,058


	December 31, 2010
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value

Corporate debt securities	$	125,708	$	1,655	$	(19	)	$	127,344
Residential mortgage-backed securities		53,944		787		(13	)		54,718
Government-sponsored enterprise securities		86,905		61		—			86,966
Asset-backed securities		12,983		5		—			12,988

Subtotal - Marketable securities		279,540		2,508		(32	)		282,016


Corporate debt securities		248,500		3,611		(881	)		251,230
Residential mortgage-backed securities		79,605		1,161		(20	)		80,746
Government-sponsored enterprise securities		25,402		3		(120	)		25,285
Asset-backed securities		58,822		84		(2	)		58,904

Subtotal - Marketable securities, non-current		412,329		4,859		(1,023	)		416,165


U.S. Treasury and agencies		1,302		10		—			1,312
Restricted cash and cash equivalents		7,455		—		—			7,455
Corporate debt securities		45,931		620		(29	)		46,522
Residential mortgage-backed securities		6,368		128		—			6,496
Government-sponsored enterprise securities		13,237		72		(6	)		13,303
Asset-backed securities		4,412		10		—			4,422

Subtotal - Restricted investments		78,705		840		(35	)		79,510


Total	$	770,574	$	8,207	$	(1,090	)	$	777,691

As of September 30, 2011, the Company's 2¹/4% Convertible Subordinated Notes due 2012 are classified as current as $206,736 becomes due within the next 12 months. The Company has classified all of its marketable securities, including those with maturities greater than one year, as current on the consolidated balance sheet, as these securities may need to be liquidated if the 2¹/4% Convertible Subordinated Notes due 2012 are repaid in cash rather than converting to common stock.

See Note 10, Fair Value Measurements, for the fair value of the Company's financial assets and liabilities.

The Company's restricted investments with respect to its headquarters ("Traville") lease serve as collateral for a letter of credit which serves as the security deposit for the duration of the lease, although the Company has the ability to reduce the restricted investments that are in the form of securities by substituting cash security deposits in the amount of $19,750 to be maintained with the landlord. Presently, to secure the security deposit letter of credit, the Company is required to maintain margin value of the collateral of at least $19,750.

The Company's restricted investments with respect to its large-scale manufacturing facility ("LSM") lease, as amended, will serve as collateral in favor of the landlord in lieu of providing the landlord with either a cash deposit or a standby letter of credit. Under the LSM lease, the Company is required to pledge to the landlord a minimum of $20,000 in marketable securities or provide the landlord with a $19,750 cash security deposit. As of September 30, 2011 and December 31, 2010, the Company has pledged marketable securities.

In addition, the Company is also required to maintain $34,300 in restricted investments with respect to two leases with the Maryland Economic Development Corporation ("MEDCO") for its small-scale manufacturing facility. The facility was financed primarily through a combination of bonds issued by MEDCO ("MEDCO Bonds") and loans issued to MEDCO by certain State of Maryland agencies. The MEDCO Bonds are secured by letters of credit issued for the account of MEDCO which expire in December 2011. The Company is required to maintain restricted investments which serve as security for the MEDCO letters of credit reimbursement obligation. The Company is currently negotiating with a lender to extend and replace the expiring letters of credit and expects to finalize the transaction prior to the expiration of the current letters of credit.

Marketable securities and Restricted investments – unrealized losses

The Company owned 340 available-for-sale securities as of September 30, 2011. Of these 340 securities, 92 had unrealized losses as of September 30, 2011. The Company did not have any investments in a loss position for greater than 12 months as of September 30, 2011. The Company's gross unrealized losses and fair value of investments with unrealized losses as of December 31, 2010 were as follows:


	December 31, 2010
	Loss Position for Less Than Twelve Months					Loss Position for Greater Than Twelve Months					Total
	Fair Value		Unrealized Losses			Fair Value		Unrealized Losses			Fair Value		Unrealized Losses

Corporate debt securities	$	35,432	$	(18	)	$	1,536	$	(1	)	$	36,968	$	(19	)
Residential mortgage-backed securities		54,718		(13	)		—		—			54,718		(13	)
Asset-backed securities		3,286		—			—		—			3,286		—

Subtotal - Marketable securities		93,436		(31	)		1,536		(1	)		94,972		(32	)


Corporate debt securities		56,992		(881	)		—		—			56,992		(881	)
Residential mortgage-backed securities		80,746		(20	)		—		—			80,746		(20	)
Government-sponsored enterprise securities		20,237		(120	)		—		—			20,237		(120	)
Asset-backed securities		8,400		(2	)		—		—			8,400		(2	)

Subtotal - Marketable securities, non-current		166,375		(1,023	)		—		—			166,375		(1,023	)


Corporate debt securities		7,110		(29	)		—		—			7,110		(29	)
Government-sponsored enterprise securities		1,502		(6	)		—		—			1,502		(6	)

Subtotal - Restricted investments		8,612		(35	)		—		—			8,612		(35	)


Total	$	268,423	$	(1,089	)	$	1,536	$	(1	)	$	269,959	$	(1,090	)

The Company has evaluated its marketable securities and restricted investments and has determined that none of these investments has an other-than-temporary impairment, as it has no intent to sell securities with unrealized losses and it is not more likely than not that the Company will be required to sell any securities with unrealized losses, given the Company's current and anticipated financial position.

The Company's equity investments of less than 20% in privately-held companies are carried at cost and are included in Other assets on the consolidated balance sheet as of December 31, 2010. As of September 30, 2011, the Company no longer owns any such investments (see Note 4, Collaborations and Other Agreements – Aegera Agreement, for additional information).

Other Information

The following table summarizes maturities of the Company's marketable securities and restricted investments as of September 30, 2011:


	Marketable Securities				Restricted Investments
	Amortized Cost		Fair Value		Amortized Cost		Fair Value

Less than one year	$	120,284	$	121,534	$	34,628	$	34,715
Due in year two through year three		307,669		310,586		40,719		40,876
Due in year four through year five		47,776		48,644		4,182		4,140
Due after five years		21,073		21,373		188		190

Total	$	496,802	$	502,137	$	79,717	$	79,921

The Company's investments in mortgage-backed securities have no single maturity date and, accordingly, have been allocated on a pro rata basis to each maturity range based on each maturity range's percentage to the total value.

Realized gains and losses on securities which are included in the Company's investment income for the three and nine months ended September 30, 2011 and 2010, and their respective net proceeds were as follows:


	Three months ended September 30,						Nine months ended September 30,
	2011			2010			2011			2010

Proceeds on sale of investments	$	96,319		$	111,421		$	422,226		$	582,015
Realized gains		341			140			521			1,618
Realized losses		(303	)		(512	)		(1,135	)		(1,379	)

The cost of the securities sold is based on the specific identification method.