Cash and Cash Equivalents and Investments

9 Months Ended

Sep. 30, 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 September 30, 2016 and December 31, 2015 are as follows:

	As of September 30, 2016
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
	(in thousands)
Cash and cash equivalents	$	38,772	$	—	$	—		$	38,772
Securities maturing within one year:
U.S. treasury securities	318,979		119		(20		)	319,078
Corporate debt securities	37,727		5		(26		)	37,706
Total short-term investments	$	356,706	$	124	$	(46	)	$	356,784
Total cash and cash equivalents and investments	$	395,478	$	124	$	(46	)	$	395,556
	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 nine months ended September 30, 2016, and no realized gains or losses for the nine months ended September 30, 2015. The cost of securities sold is based on the specific identification method.