Cash and Cash Equivalents and Investments

3 Months Ended

Mar. 31, 2012

Cash and Cash Equivalents and Investments [Abstract]

Cash and Cash Equivalents Disclosure

Cash and Cash Equivalents and Investments

The fair value of cash and cash equivalents and investments held at March 31, 2012 and December 31, 2011 are as follows:

	As of March 31, 2012
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
	(in thousands)
Cash and cash equivalents	$	29,010	$	—	$	—		$	29,010
Securities maturing within one year:
Certificates of deposit	548		—		—			548
U.S. treasury securities	224,155		3		(60		)	224,098
Total short-term investments	$	224,703	$	3	$	(60	)	$	224,646
Total cash and cash equivalents and investments	$	253,713	$	3	$	(60	)	$	253,656
	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

There were no realized gains or losses for the three months ended March 31, 2012 and 2011. The cost of securities sold is based on the specific identification method.