A summary of cash, cash equivalents and available-for-sale marketable securities held by the Company as of March 31, 2019 and December 31, 2018 is as follows (in thousands):


	March 31, 2019
			Unrealized		Unrealized		Fair
	Cost		gains		losses		value

Cash and cash equivalents:
Cash (Level 1)	$	2,075	$	—	$	—	$	2,075
Money market funds (Level 1)		45,418		—		—		45,418
Corporate debt securities due within 3 months of date of purchase (Level 2)		—		—		—		—
Total cash and cash equivalents		47,493		—		—		47,493
Marketable securities:
Corporate debt securities due within 1 year of date of purchase (Level 2)		430,154		189		(11)		430,332
Total cash, cash equivalents and marketable securities	$	477,647	$	189	$	(11)	$	477,825


	December 31, 2018
			Unrealized		Unrealized		Fair
	Cost		gains		losses		value

Cash and cash equivalents:
Cash (Level 1)	$	2,004	$	—	$	—	$	2,004
Money market funds (Level 1)		43,401		—		—		43,401
Corporate debt securities due within 3 months of date of purchase (Level 2)		11,974		—		—		11,974
Total cash and cash equivalents		57,379		—		—		57,379
Marketable securities:
Corporate debt securities due within 1 year of date of purchase (Level 2)		426,658		14		(333)		426,339
Total cash, cash equivalents and marketable securities	$	484,037	$	14	$	(333)	$	483,718