Cash and Cash Equivalents and Investments

12 Months Ended

Dec. 31, 2016

Cash and Cash Equivalents and Investments [Abstract]

Cash and Cash Equivalents and Investments

Cash and Cash Equivalents and Investments

The fair value of cash and cash equivalents and investments held at December 31, 2016 and 2015 are as follows:

	As of December 31, 2016
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
			(in thousands)
Cash and cash equivalents	$	46,600	$	—	$	—		$	46,600
Securities maturing within one year:
U.S. treasury securities	227,911		1		(107		)	227,805
Corporate debt securities	72,188		1		(90		)	72,099
Total short-term investments	$	300,099	$	2	$	(197	)	$	299,904
Total cash and cash equivalents and investments	$	346,699	$	2	$	(197	)	$	346,504

	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 year ended December 31, 2016, no realized gains or losses for the year ended December 31, 2015, and no realized gains or losses for the year ended December 31, 2014.