Cash and available for sale securities consisted of the following as of December 31, 2017 and December 31, 2016 (in thousands):

	As of December 31, 2017
	Cost		Unrealized Gain		Unrealized Loss			Fair Value
Cash balances	$	49,060	$	—	$	—		$	49,060
Corporate debt securities, current portion		199,314		1		(303	)		199,012
Commercial paper		79,878		—		(75	)		79,803
Asset-backed securities		30,346		—		(59	)		30,287
Money market		350		—		—			350
Certificate of deposit		50		—		—			50

	$	358,998	$	1	$	(437	)	$	358,562


Included in cash and cash equivalents	$	49,060	$	—	$	—		$	49,060
Included in marketable securities		309,938		1		(437	)		309,502

Total cash and marketable securities	$	358,998	$	1	$	(437	)	$	358,562

	As of December 31, 2016
	Cost		Unrealized Gain		Unrealized Loss			Fair Value
Cash balances	$	187,026	$	—	$	—		$	187,026
Corporate debt securities, current portion		74,564		2		(31	)		74,535
Commercial paper		68,258		132		—			68,390
Money market		350		—		—			350
Certificate of deposit		50		—		—			50

	$	330,248	$	134	$	(31	)	$	330,351


Included in cash and cash equivalents	$	187,026	$	—	$	—		$	187,026
Included in marketable securities		143,222		134		(31	)		143,325

Total cash and marketable securities	$	330,248	$	134	$	(31	)	$	330,351