
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value
Short-term debt securities:
U.S. agency securities	$	173,424	$	912	$	(208)	$	174,128
Corporate bonds	75,440		50		(627)		74,863
Commercial paper	2,996		—		—		2,996
Municipal securities	8,837		44		(5)		8,876
U.S. government securities	238,012		1,722		(114)		239,620
Foreign securities	21,308		52		(3)		21,357
Total	$	520,017	$	2,780	$	(957)	$	521,840

Long-term debt securities:
U.S. agency securities	$	166,075	$	704	$	(466)	$	166,313
Corporate bonds	141,920		216		(2,161)		139,975
Municipal securities	8,464		32		(40)		8,456
U.S. government securities	177,308		2,648		(587)		179,369
Foreign securities	35,031		334		(18)		35,347
Total	$	528,798	$	3,934	$	(3,272)	$	529,460


	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value
Short-term debt securities:
U.S. agency securities	$	131,124	$	409	$	(11)	$	131,522
Corporate bonds	67,169		580		(28)		67,721

Municipal securities	6,667		109		—		6,776
U.S. government securities	264,069		1,083		(17)		265,135
Foreign securities	21,270		48		(16)		21,302
Total	$	490,299	$	2,229	$	(72)	$	492,456

Long-term debt securities:
U.S. agency securities	$	63,645	$	612	$	(189)	$	64,068
Corporate bonds	141,307		1,832		(61)		143,078
Municipal securities	9,594		151		(39)		9,706
U.S. government securities	294,682		1,287		(190)		295,779
Foreign securities	24,625		86		(39)		24,672
Total	$	533,853	$	3,968	$	(518)	$	537,303

The Company's gross unrealized losses and fair values for those investments that were in an unrealized loss position as of March 31, 2020 and December 31, 2019, aggregated by investment category and the length of time that individual securities have been in a continuous loss position are as follows (in thousands):


	March 31, 2020
	Less than 12 months						Greater than 12 months						Total
	Fair Value		Gross Unrealized Losses		Fair Value		Gross Unrealized Losses		Fair Value		Gross Unrealized Losses
Short-term debt securities:
U.S. agency securities	$	26,172	$	(208)	$	—	$	—	$	26,172	$	(208)
Corporate bonds	61,012		(627)		—		—		61,012		(627)
Municipal securities	5,342		(5)		—		—		5,342		(5)
U.S. government securities	24,028		(114)		—		—		24,028		(114)
Foreign securities	4,209		(3)		—		—		4,209		(3)
Total	$	120,763	$	(957)	$	—	$	—	$	120,763	$	(957)

Long-term debt securities:
U.S. agency securities	$	23,037	$	(466)	$	—	$	—	$	23,037	$	(466)
Corporate bonds	106,455		(2,161)		—		—		106,455		(2,161)
Municipal securities	489		(40)		—		—		489		(40)
U.S. government securities	9,061		(587)		—		—		9,061		(587)
Foreign securities	2,003		(18)		—		—		2,003		(18)
Total	$	141,045	$	(3,272)	$	—	$	—	$	141,045	$	(3,272)


	December 31, 2019
	Less than 12 months						Greater than 12 months						Total
	Fair Value		Gross Unrealized Losses		Fair Value		Gross Unrealized Losses		Fair Value		Gross Unrealized Losses
Short-term debt securities:
U.S. agency securities	$	23,896	$	(9)	$	4,996	$	(2)	$	28,892	$	(11)
Corporate bonds	5,507		(27)		2,502		(1)		8,009		(28)
U.S. government securities	21,481		(8)		14,984		(9)		36,465		(17)
Foreign securities	13,499		(16)		—		—		13,499		(16)
Total	$	64,383	$	(60)	$	22,482	$	(12)	$	86,865	$	(72)

Long-term debt securities:
U.S. agency securities	$	16,740	$	(189)	$	—	$	—	$	16,740	$	(189)
Corporate bonds	16,708		(61)		—		—		16,708		(61)
Municipal securities	1,005		(39)		—		—		1,005		(39)
U.S. government securities	42,210		(162)		—		(28)		42,210		(190)
Foreign securities	16,383		(39)		—		—		16,383		(39)
Total	$	93,046	$	(490)	$	—	$	(28)	$	93,046	$	(518)

The unrealized losses above were as a consequence of interest rate changes. The U.S. government and U.S. agency securities are either explicitly or implicitly guaranteed by the U.S. government and are highly rated by major rating agencies. The corporate bonds are issued by highly rated entities. The non-US government securities are issued by highly rated international entities. The Company has the ability and intent to hold these investments with unrealized losses for a reasonable period of time sufficient for the recovery of their amortized cost bases, which may be at maturity. The Company determines any realized gains or losses on the sale of marketable debt securities on a specific identification method, and records such gains and losses as a component of other expense, net.


	March 31, 2020		December 31, 2019
Cash	$	132,908	$	422,459
Cash Equivalents:
Money market funds	505,553		233
U.S. agency securities	9,999		8,585
U.S. government securities	—		6,984
Short-term debt securities:
U.S. agency securities	118,835		—
U.S. government securities	177,516		238,031
Total	$	944,811	$	676,292


	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value
Short-term debt securities:
U.S. agency securities	$	118,750	$	100	$	(15)	$	118,835
U.S. government securities	176,750		821		(55)		177,516
Total	$	295,500	$	921	$	(70)	$	296,351


	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value
Short-term debt securities:

U.S. government securities	$	237,909	$	144	$	(22)	$	238,031
Total	$	237,909	$	144	$	(22)	$	238,031

The gross unrealized losses and fair values for those investments that were in an unrealized loss position as of March 31, 2020 and December 31, 2019, aggregated by investment category and the length of time that individual securities have been in a continuous loss position are as follows (in thousands):


	March 31, 2020
	Less than 12 months						Greater than 12 months						Total
	Fair Value		Gross Unrealized Losses		Fair Value		Gross Unrealized Losses		Fair Value		Gross Unrealized Losses
Short-term debt securities:
U.S. agency securities	$	39,934	$	(15)	$	—	$	—	$	39,934	$	(15)
U.S. government securities	3,999		(55)		—		—		3,999		(55)
Total	$	43,933	$	(70)	$	—	$	—	$	43,933	$	(70)


	December 31, 2019
	Less than 12 months						Greater than 12 months						Total
	Fair Value		Gross Unrealized Losses		Fair Value		Gross Unrealized Losses		Fair Value		Gross Unrealized Losses
Short-term debt securities:
U.S. government securities	$	56,984	$	(22)	$	—	$	—	$	56,984	$	(22)
Total	$	56,984	$	(22)	$	—	$	—	$	56,984	$	(22)

The unrealized losses above were caused by interest rate changes. The U.S. government securities are either explicitly or implicitly guaranteed by the U.S. government and are highly rated by major rating agencies. The Company has the ability and intent to hold these investments with unrealized losses for a reasonable period of time sufficient for the recovery of their amortized cost bases, which may be at maturity. The Company determines any realized gains or losses on the sale of marketable debt securities on a specific identification method, and records such gains and losses as a component of other expense, net.