Cash and Cash Equivalents and Investments

3 Months Ended

Mar. 31, 2016

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, 2016 and December 31, 2015 are as follows:

	As of March 31, 2016
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
	(in thousands)
Cash and cash equivalents	$	24,681	$	—	$	—		$	24,681
Securities maturing within one year:
U.S. treasury securities	434,505		305		(7		)	434,803
Corporate debt securities	17,663		2		(3		)	17,662
Total short-term investments	$	452,168	$	307	$	(10	)	$	452,465
Total cash and cash equivalents and investments	$	476,849	$	307	$	(10	)	$	477,146
	As of December 31, 2015
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
			(in thousands)
Cash and cash equivalents	$	202,989	$	—	$	—		$	202,989
Securities maturing within one year:
U.S. treasury securities	313,105		2		(219		)	312,888
Corporate debt securities	5,477		—		(2		)	5,475
Total short-term investments	$	318,582	$	2	$	(221	)	$	318,363
Total cash and cash equivalents and investments	$	521,571	$	2	$	(221	)	$	521,352

There were no realized gains or losses for the three months ended March 31, 2016, and no realized gains or losses for the three months ended March 31, 2015. The cost of securities sold is based on the specific identification method.