Marketable securities (Details) $ in Thousands	3 Months Ended
Mar. 31, 2020 USD ($) security	Dec. 31, 2019 USD ($)
Marketable securities
Amortized Cost	$ 17,980	$ 37,414
Gross Unrealized Gains		25
Gross Unrealized Losses	(4)
Marketable securities	$ 17,976	37,439
Number of securities in an unrealized loss position \| security	3
Aggregate fair value of securities in an unrealized loss position	$ 8,993
Change in credit loss	0
Allowance for credit loss	0
Commercial paper
Marketable securities
Amortized Cost	5,983	11,940
Marketable securities	5,983	11,940
Corporate bonds
Marketable securities
Amortized Cost	11,997	11,990
Gross Unrealized Gains		20
Gross Unrealized Losses	(4)
Marketable securities	$ 11,993	12,010
U.S. Treasuries
Marketable securities
Amortized Cost		13,484
Gross Unrealized Gains		5
Marketable securities		$ 13,489

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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