AVAILABLE-FOR-SALE SECURITIES (Tables)

6 Months Ended

Jun. 30, 2013

AVAILABLE-FOR-SALE SECURITIES

Schedule of amortized cost and estimated fair values for available-for-sale securities

	June 30, 2013
(in thousands)	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
U.S. government securities	$	27,101	$	15	$	—		$	27,116
U.S. government agencies	157,932		48		(51		)	157,929
U.S. corporate notes	104,098		15		(42		)	104,071
U.S. commercial paper	44,967		—		—			44,967
Money market funds	192,694		—		—			192,694
Total	$	526,792	$	78	$	(93	)	$	526,777

	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

Schedule of classification of the available-for-sale debt securities

(in thousands)	June 31, 2013		December 31, 2012
Cash and cash equivalents	$	191,862	$	86,298
Short-term investments	243,768		153,640
Long-term marketable securities	90,314		95,194
Restricted cash	833		833
Total	$	526,777	$	335,965