Marketable securities

12 Months Ended

Dec. 31, 2019

Investments, Debt and Equity Securities [Abstract]

Marketable securities

Marketable securitiesThe following table summarizes the marketable securities held at December 31, 2019 and 2018 (in thousands):

	Amortized cost / cost		Unrealized gains		Unrealized losses		Fair value
December 31, 2019
U.S. government agency securities and treasuries	$	633,970	$	2,014	$	(48)	$	635,936
Certificates of deposit	960		—		—		960
Corporate bonds	185,827		824		(43)		186,608
Commercial paper	74,378		—		—		74,378
Equity securities	20,017		—		(7,147)		12,870
Total	$	915,152	$	2,838	$	(7,238)	$	910,752
December 31, 2018
U.S. government agency securities and treasuries	$	1,459,649	$	963	$	(3,011)	$	1,457,601
Certificates of deposit	9,080		—		—		9,080
Equity securities	20,017		2,150		—		22,167
Total	$	1,488,746	$	3,113	$	(3,011)	$	1,488,848

No available-for-sale debt securities held as of December 31, 2019 or 2018 had remaining maturities greater than three years.