2. INVESTMENTS

Available-for-sale securities are carried at fair value, with the unrealized gains and losses reported in comprehensive loss. The amortized cost of debt securities in this category is adjusted for amortization of premiums and accretion of discounts to maturity. Such amortization is included in interest income. Realized gains and losses and declines in value judged to be other-than-temporary, if any, on available-for-sale securities are included in other income or expense. The cost of securities sold is based on the specific identification method. Interest and dividends on securities classified as available-for-sale are included in interest income.

Investments consist of the following (in thousands):


	March 31, 2014		December 31, 2013
Certificates of deposit	$	11,217	$	11,012
Commercial paper		19,964		4,997
Corporate debt securities		121,940		77,441
Securities of government sponsored entities		12,529		7,500

Total investments	$	165,650	$	100,950

The following is a summary of investments classified as available-for-sale securities (in thousands):


	Contractual Maturity (in years)		Amortized Cost		Gross Unrealized Gains(1)		Gross Unrealized Losses(1)			Aggregate Estimated Fair Value
March 31, 2014:
Classified as current assets:
Certificates of deposit		Less than 1	$	9,791	$	1	$	(11	)	$	9,781
Commercial paper		Less than 1		19,968		1		(5	)		19,964
Corporate debt securities		Less than 1		72,094		8		(46	)		72,056
Securities of government sponsored entities		Less than 1		12,531		—		(2	)		12,529

Total short-term available for sale securities			$	114,384	$	10	$	(64	)	$	114,330
Classified as long-term assets:
Certificates of deposit		1-2		1,440		—		(4	)		1,436
Corporate debt securities		1-2		50,020		—		(136	)		49,884

Total long-term available for sale securities				51,460		—		(140	)		51,320

Total available-for-sale securities			$	165,844	$	10	$	(204	)	$	165,650

December 31, 2013:
Classified as current assets:
Certificates of deposit		Less than 1	$	11,018	$	1	$	(7	)	$	11,012
Commercial paper		Less than 1		4,997		—		—			4,997
Corporate debt securities		Less than 1		77,430		19		(8	)		77,441
Securities of government sponsored entities		Less than 1		7,500		—		—			7,500

Total short-term available for sale securities			$	100,945	$	20	$	(15	)	$	100,950

(1)	Unrealized gains and losses are included in other comprehensive loss.

The following table presents information about available-for-sale investments in an unrealized loss position (in thousands):


	Less Than 12 Months					12 Months or Greater				Total
	Estimated Fair Value		Unrealized Losses			Estimated Fair Value		Unrealized Losses		Estimated Fair Value		Unrealized Losses
March 31, 2014:
Certificates of deposit	$	9,296	$	(15	)	$	—	$	—	$	9,296	$	(15	)
Commercial paper		11,969		(5	)		—		—		11,969		(5	)
Corporate debt securities		82,745		(182	)		—		—		82,745		(182	)
Securities of government sponsored entities		5,029		(2	)		—		—		5,029		(2	)

Total	$	109,039	$	(204	)	$	—	$	—	$	109,039	$	(204	)

December 31, 2013:
Certificates of deposit	$	9,802	$	(7	)	$	—	$	—	$	9,802	$	(7	)
Corporate debt securities		29,919		(8	)		—		—		29,919		(8	)

Total	$	39,721	$	(15	)	$	—	$	—	$	39,721	$	(15	)