Cash and Cash Equivalents and Investments (Tables)

6 Months Ended

Jun. 30, 2012

Cash and Cash Equivalents and Investments [Abstract]

Schedule of Cash, Cash Equivalents and Short-term Investments [Table Text Block]

	As of June 30, 2012
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
	(in thousands)
Cash and cash equivalents	$	33,779	$	—	$	—		$	33,779
Securities maturing within one year:
Certificates of deposit	548		—		—			548
U.S. treasury securities	197,206		6		(26		)	197,186
Total short-term investments	$	197,754	$	6	$	(26	)	$	197,734
Total cash and cash equivalents and investments	$	231,533	$	6	$	(26	)	$	231,513
	As of December 31, 2011
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
			(in thousands)
Cash and cash equivalents	$	186,309	$	—	$	—		$	186,309
Securities maturing within one year:
Certificates of deposit	548		—		—			548
U.S. treasury securities	94,814		24		(3		)	94,835
Total short-term investments	$	95,362	$	24	$	(3	)	$	95,383
Total cash and cash equivalents and investments	$	281,671	$	24	$	(3	)	$	281,692