Cash and Cash Equivalents and Investments

12 Months Ended

Dec. 31, 2011

Cash and Cash Equivalents and Investments [Abstract]

Cash and Cash Equivalents and Investments

Cash and Cash Equivalents and Investments

The fair value of cash and cash equivalents and investments held at December 31, 2011 and 2010 are as follows:

	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

	As of December 31, 2010
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
			(in thousands)
Cash and cash equivalents	$	47,207	$	1	$	—		$	47,208
Securities maturing within one year:
Certificates of deposit	545		—		—			545
U.S. treasury securities	163,354		10		(6		)	163,358
Total short-term investments	$	163,899	$	10	$	(6	)	$	163,903
Total cash and cash equivalents and investments	$	211,106	$	11	$	(6	)	$	211,111

There were no realized gains or losses for the years ended December 31, 2011, 2010 and 2009.