Cash and Cash Equivalents and Investments

6 Months Ended

Jun. 30, 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 June 30, 2013 and December 31, 2012 are as follows:

	As of June 30, 2013
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
	(in thousands)
Cash and cash equivalents	$	23,254	$	—	$	—		$	23,254
Securities maturing within one year:
Certificates of deposit	551		—		—			551
U.S. treasury securities	151,542		31		—			151,573
Total short-term investments	$	152,093	$	31	$	—		$	152,124
Total cash and cash equivalents and investments	$	175,347	$	31	$	—		$	175,378
	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 six months ended June 30, 2013, and no realized gains or losses for the six months ended June 30, 2012. The cost of securities sold is based on the specific identification method.