Marketable Securities (Tables)

6 Months Ended

Jun. 30, 2011

Marketable Securities [Abstract]

Summary of Available-for-sale marketable securities

	June 30, 2011
	Adjusted		Unrealized		Unrealized			Estimated
	Cost		Gains		Losses			Fair Value
	(In thousands)
Agency bond investments:
Current	$	158,431	$	102	$	(23	)	$	158,510
Total agency bond investments		158,431		102		(23	)		158,510
Corporate debt investments:
Current		246,011		155		(32	)		246,134
Non-current		29,225		—		(1,172	)		28,053
Total corporate investments		275,236		155		(1,204	)		274,187
Total available-for-sale marketable securities	$	433,667	$	257	$	(1,227	)	$	432,697

	December 31, 2010
	Adjusted		Unrealized		Unrealized			Estimated
	Cost		Gains		Losses			Fair Value
	(In thousands)
Agency bond investments:
Current	$	178,221	$	18	$	(29	)	$	178,210
Total agency bond investments		178,221		18		(29	)		178,210
Corporate debt investments:
Current		237,547		175		(24	)		237,698
Non-current		29,925		—		(1,370	)		28,555
Total corporate investments		267,472		175		(1,394	)		266,253
Total available-for-sale marketable securities	$	445,693	$	193	$	(1,423	)	$	444,463