Cash and Cash Equivalents and Investments

3 Months Ended

Mar. 31, 2013

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, 2013 and December 31, 2012 are as follows:

	As of March 31, 2013
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
	(in thousands)
Cash and cash equivalents	$	34,248	$	—	$	—		$	34,248
Securities maturing within one year:
Certificates of deposit	550		—		—			550
U.S. treasury securities	162,323		42		—			162,365
Total short-term investments	$	162,873	$	42	$	—		$	162,915
Total cash and cash equivalents and investments	$	197,121	$	42	$	—		$	197,163
	As of December 31, 2012
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
			(in thousands)
Cash and cash equivalents	$	30,423	$	—	$	—		$	30,423
Securities maturing within one year:
Certificates of deposit	551		—		—			551
U.S. treasury securities	192,211		24		(1		)	192,234
Total short-term investments	$	192,762	$	24	$	(1	)	$	192,785
Total cash and cash equivalents and investments	$	223,185	$	24	$	(1	)	$	223,208

There were no realized gains or losses for the three months ended March 31, 2013, and no realized gains or losses for the three months ended March 31, 2012. The cost of securities sold is based on the specific identification method.