Marketable Securities, Available-for-sale (Tables)

6 Months Ended

Jun. 30, 2013

Marketable Securities, Available-for-sale

Fair value of the available-for-sale marketable securities, by type of security

								JUNE 30, 2013
			GROSS		GROSS
	AMORTIZED		UNREALIZED		UNREALIZED			ESTIMATED
(in thousands)	COST		GAINS		LOSSES			FAIR VALUE
Type of security:
U.S. Treasury securities	$	42,689	$	1	$	(26	)	$	42,664
Obligations of U.S. and local government agencies	65,265		492		(752		)	65,005
Corporate debt securities	158,846		29		(235		)	158,640
Asset-backed securities	28,251		81		(292		)	28,040
Total debt securities	295,051		603		(1,305		)	294,349
Short-term pooled investments	67,864		-		(19		)	67,845
Total marketable securities, available-for-sale	$	362,915	$	603	$	(1,324	)	$	362,194
					DECEMBER 31, 2012
Type of security:
U.S. Treasury securities	$	3,098	$	1	$	-		$	3,099
Obligations of U.S. and local government agencies	154,774		1,008		(489		)	155,293
Corporate debt securities	165,153		116		(75		)	165,194
Asset-backed securities	27,325		153		(164		)	27,314
Total debt securities	350,350		1,278		(728		)	350,900
Short-term pooled investments	37,127		-		(7		)	37,120
Total marketable securities, available-for-sale	$	387,477	$	1,278	$	(735	)	$	388,020

Fair value of the available-for-sale marketable securities, by contractual maturity

(in thousands)	JUNE 30, 2013		DECEMBER 31, 2012
Contractual maturity:
Maturing in one year or less	$	113,328	$	68,347
Maturing after one year through three years	153,707		257,595
Maturing after three years	27,314		24,958
Total debt securities	294,349		350,900
Short-term pooled investments	67,845		37,120
Total marketable securities, available-for-sale	$	362,194	$	388,020