INVESTMENTS (Tables)

6 Months Ended

Jun. 30, 2013

INVESTMENTS

Amortized cost and estimated fair value of marketable securities, which are considered to be available-for-sale investments

	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
	(in thousands)
Balance as of June 30, 2013
Bank deposits	$	116,902	$	—	$	—		$	116,902
U.S. Treasury securities	93,034		6		(2		)	93,038
Corporate and municipal notes	573,730		32		(539		)	573,223
Total	$	783,666	$	38	$	(541	)	$	783,163
Balance as of December 31, 2012
Bank deposits	$	61,000	$	—	$	—		$	61,000
U.S. Treasury securities	114,041		4		(3		)	114,042
Corporate and municipal notes	640,234		158		(215		)	640,177
Total	$	815,275	$	162	$	(218	)	$	815,219

Contractual maturities of marketable securities

	June 30, 2013				December 31, 2012
	Amortized Cost		Fair Value		Amortized Cost		Fair Value
	(in thousands)
Within 1 year	$	673,224	$	673,080	$	812,104	$	812,052
1-2 years	110,442		110,083		3,171		3,167
Total	$	783,666	$	783,163	$	815,275	$	815,219