Cash and Cash Equivalents and Investments

6 Months Ended

Jun. 30, 2015

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, 2015 and December 31, 2014 are as follows:

	As of June 30, 2015
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
	(in thousands)
Cash and cash equivalents	$	9,744	$	—	$	—		$	9,744
Securities maturing within one year:
Certificates of deposit	553		—		—			553
U.S. treasury securities	272,088		1,241		(1,143		)	272,186
Total short-term investments	$	272,641	$	1,241	$	(1,143	)	$	272,739
Total cash and cash equivalents and investments	$	282,385	$	1,241	$	(1,143	)	$	282,483
	As of December 31, 2014
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
			(in thousands)
Cash and cash equivalents	$	137,266	$	—	$	—		$	137,266
Securities maturing within one year:
Certificates of deposit	552		—		—			552
U.S. treasury securities	201,584		3		(66		)	201,521
Total short-term investments	$	202,136	$	3	$	(66	)	$	202,073
Total cash and cash equivalents and investments	$	339,402	$	3	$	(66	)	$	339,339

There were no realized gains or losses for the six months ended June 30, 2015, and no realized gains or losses for the six months ended June 30, 2014. The cost of securities sold is based on the specific identification method.