Cash, Cash Equivalents and Marketable Securities (Tables)

12 Months Ended

Dec. 31, 2015

Cash, Cash Equivalents and Marketable Securities

Schedule of reconciliation of cash, cash equivalents and marketable securities from amortized cost to fair value

        The following tables summarize the Company's cash, cash equivalents and marketable securities as of December 31, 2015 and December 31, 2014 (in thousands):

As of December 31, 2015	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
Cash, money market funds and overnight repurchase agreements	$	61,461	$	—	$	—		$	61,461
U.S. government-sponsored enterprise securities due in one year or less		24,285		5		—			24,290
Corporate debt securities due in one year or less		73,735		1		(84	)		73,652
Commercial paper obligations due in one year or less		125,693		120		(8	)		125,805
Asset-backed securities due in one year or less		64,866		—		(30	)		64,836
Total	$	350,040	$	126	$	(122	)	$	350,044
Reported as:
Cash and cash equivalents	$	61,461	$	—	$	—		$	61,461
Marketable securities		288,579		126		(122	)		288,583
Total	$	350,040	$	126	$	(122	)	$	350,044

As of December 31, 2014	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
Cash and money market funds	$	60,369	$	—	$	—		$	60,369
Corporate debt securities due in one year or less		71,669		3		(24	)		71,648
Commercial paper obligations due in one year or less		15,237		13		—			15,250
Foreign government bonds due in one year or less		18,519		2		(1	)		18,520
Asset-backed securities due in one year or less		25,751		—		(9	)		25,742
Total	$	191,545	$	18	$	(34	)	$	191,529
Reported as:
Cash and cash equivalents	$	61,349	$	—	$	—		$	61,349
Marketable securities		130,196		18		(34	)		130,180
Total	$	191,545	$	18	$	(34	)	$	191,529

Schedule of aggregate fair value and unrealized losses on marketable securities

        The following table summarizes the aggregate fair value of these securities at December 31, 2015 and December 31, 2014 (in thousands):

	As of December 31, 2015					As of December 31, 2014
	Aggregate Fair Value		Unrealized Losses			Aggregate Fair Value		Unrealized Losses
Corporate debt securities due in one year or less	$	70,657	$	(84	)	$	63,221	$	(24	)
Commercial paper obligations due in one year or less	$	33,734	$	(8	)	$	—	$	—
Asset-backed securities due in one year or less	$	61,337	$	(30	)	$	25,742	$	(9	)
Foreign government bonds due in one year or less	$	—	$	—		$	12,773	$	(1	)