Marketable Securities (Tables)

9 Months Ended

Sep. 30, 2012

Marketable Securities

Summary of available-for-sale marketable securities

	September 30, 2012
	Adjusted		Unrealized		Unrealized			Estimated
	Cost		Gains		Losses			Fair Value
	(In thousands)
Agency bond investments:
Current	$	129,711	$	75	$	—		129,786
Total agency bond investments	129,711		75		—			129,786
Corporate debt investments:
Current	251,956		406		(11		)	252,351
Non-current	18,875		—		(636		)	18,239
Total corporate investments	270,831		406		(647		)	270,590
Total available-for-sale marketable securities	400,542		481		(647		)	400,376

	December 31, 2011
	Adjusted		Unrealized		Unrealized			Estimated
	Cost		Gains		Losses			Fair Value
	(In thousands)
Agency bond investments:
Current	$	187,709	$	70	$	(7	)	187,772
Total agency bond investments	187,709		70		(7		)	187,772
Corporate debt investments:
Current	315,522		128		(430		)	315,220
Non-current	23,875		—		(1,773		)	22,102
Total corporate investments	339,397		128		(2,203		)	337,322
Total available-for-sale marketable securities	527,106		198		(2,210		)	525,094