Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2019

Fair Value Disclosures [Abstract]

Assets and liabilities measured at fair value

Assets and liabilities measured at fair value at each balance sheet date are as follows (in thousands):

	December 31, 2019
	Level 1		Level 2		Level 3		Total
Assets:
Cash equivalents:
Money market funds	$	54,163	$	—	$	—	$	54,163
U.S. government treasuries	15,989		—		—		15,989
Short-term marketable securities:
U.S. government treasuries	250,070		—		—		250,070
U.S. government agency securities	—		2,000		—		2,000
Corporate debt securities	—		53,479		—		53,479
Commercial paper	—		30,358		—		30,358
Long-term marketable securities:
U.S. government treasuries	13,869		—		—		13,869
Corporate debt securities	—		26,017		—		26,017
Foreign currency derivative contracts	—		85		—		85
Total	$	334,091	$	111,939	$	—	$	446,030
Liabilities:
Foreign currency derivative contracts	$	—	$	8	$	—	$	8
Total	$	—	$	8	$	—	$	8

	December 31, 2018
	Level 1		Level 2		Level 3		Total
Assets:
Cash equivalents
Money market funds	$	42,225	$	—	$	—	$	42,225
U.S. government treasuries	1,499		—		—		1,499
Commercial paper	—		9,979		—		9,979
Short-term marketable securities:
U.S. government treasuries	219,754		—		—		219,754
U.S. government agency securities	—		73,151		—		73,151
Corporate debt securities	—		71,675		—		71,675
Commercial paper	—		22,594		—		22,594
Long-term marketable securities:
U.S. government treasuries	117,131		—		—		117,131
U.S. government agency securities	—		1,977		—		1,977
Corporate debt securities	—		28,773		—		28,773
Foreign currency derivative contracts	—		14		—		14
Total	$	380,609	$	208,163	$	—	$	588,772
Liabilities:
Foreign currency derivative contracts	$	—	$	182	$	—	$	182
Total	$	—	$	182	$	—	$	182