Marketable Securities, Available-for-sale (Tables)

3 Months Ended

Mar. 31, 2013

Marketable Securities, Available-for-sale

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

								MARCH 31, 2013
(in thousands)	AMORTIZED COST		GROSS UNREALIZED GAINS		GROSS UNREALIZED LOSSES			ESTIMATED FAIR VALUE
Type of security:
U.S. Treasury securities	$	29,471	$	16	$	-		$	29,487
Obligations of U.S. and local government agencies	92,006		922		(495		)	92,433
Corporate debt securities	197,029		152		(148		)	197,033
Asset-backed securities	38,615		161		(192		)	38,584
Total debt securities	357,121		1,251		(835		)	357,537
Short-term pooled investments	5,521		-		-			5,521
Total marketable securities, available-for-sale	$	362,642	$	1,251	$	(835	)	$	363,058
					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)	MARCH 31, 2013		DECEMBER 31, 2012
Contractual maturity:
Maturing in one year or less	$	132,831	$	68,347
Maturing after one year through three years	193,212		257,595
Maturing after three years	31,494		24,958
Total debt securities	357,537		350,900
Short-term pooled investments	5,521		37,120
Total marketable securities, available-for-sale	$	363,058	$	388,020