Marketable Securities (Tables)

3 Months Ended

Mar. 31, 2013

Marketable Securities

Summary of available-for-sale marketable securities

	March 31, 2013
	Adjusted		Unrealized		Unrealized			Estimated
	Cost		Gains		Losses			Fair Value
	(In thousands)
Agency bond investments:
Current	$	100,320	$	82	$	—		$	100,402
Total agency bond investments	$	100,320	$	82	$	—		$	100,402
Corporate debt investments:
Current	$	193,598	$	184	$	(27	)	$	193,755
Non-current	8,375		—		(197		)	8,178
Total corporate investments	$	201,973	$	184	$	(224	)	$	201,933
Total available-for-sale marketable securities	$	302,293	$	266	$	(224	)	$	302,335

	December 31, 2012
	Adjusted		Unrealized		Unrealized			Estimated
	Cost		Gains		Losses			Fair Value
	(In thousands)
Agency bond investments:
Current	$	107,673	$	65	$	—		$	107,738
Total agency bond investments	$	107,673	$	65	$	—		$	107,738
Corporate debt investments:
Current	$	223,192	$	269	$	(7	)	$	223,454
Non-current	8,575		—		(252		)	8,323
Total corporate investments	$	231,767	$	269	$	(259	)	$	231,777
Total available-for-sale marketable securities	$	339,440	$	334	$	(259	)	$	339,515