AVAILABLE-FOR-SALE SECURITIES

9 Months Ended

Sep. 30, 2013

AVAILABLE-FOR-SALE SECURITIES

AVAILABLE-FOR-SALE SECURITIES

4. AVAILABLE-FOR-SALE SECURITIES

The estimated fair value of available-for-sales securities is based on quoted market prices for these or similar investments that were based on prices obtained from a commercial pricing service. Available-for-sale securities are summarized below:

	September 30, 2013
(In thousands)	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
U.S. government securities	$	42,169	$	60	$	—		$	42,229
U.S. government agencies	161,751		107		(1		)	161,857
U.S. corporate notes	103,773		43		(7		)	103,809
U.S. commercial paper	133,818		—		—			133,818
Money market funds	146,459		—		—			146,459
Total	$	587,970	$	210	$	(8	)	$	588,172

	December 31, 2012
(In thousands)	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
U.S. government securities	$	27,197	$	10	$	(2	)	$	27,205
U.S. government agencies	115,397		85		(16		)	115,466
U.S. corporate notes	91,544		32		(10		)	91,566
U.S. commercial paper	23,082		—		—			23,082
Money market funds	78,646		—		—			78,646
Total	$	335,866	$	127	$	(28	)	$	335,965

The following table summarizes the classification of the available-for-sale securities on the Company’s condensed consolidated balance sheets:

(In thousands)	September 30, 2013		December 31, 2012
Cash and cash equivalents	$	164,745	$	86,298
Short-term investments	334,261		153,640
Marketable securities	88,333		95,194
Restricted cash	833		833
Total	$	588,172	$	335,965

At September 30, 2013, all of the marketable securities have contractual maturities within two years and the average duration of marketable securities was approximately eight months. The Company does not intend to sell the investments which are in an unrealized loss position, and it is unlikely that the Company will be required to sell the investments before recovery of their amortized cost basis, which may be maturity. The Company has determined that the gross unrealized losses on its marketable securities at September 30, 2013, were temporary in nature. All marketable securities with unrealized losses have been in a loss position for less than twelve months.