Cash, cash equivalents, restricted cash and available-for-sale marketable securities (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Dec. 31, 2020	Mar. 31, 2020
Amortized Cost
Cash and cash equivalents	$ 117,799	$ 104,440	$ 165,227
Marketable securities, amortized cost	36,466	71,568
Total money market funds and marketable securities	145,621	175,560
Fair Value
Marketable securities, fair value	43,707	76,698
Total money market funds and marketable securities	152,862	180,690
Unrealized Gains and Losses
Marketable securities, unrealized gains	7,241	5,136
Total money market funds and marketable securities	$ 7,241	5,136
Marketable securities, unrealized losses		6
Total money market funds and marketable securities		6
Debt securities, contractual maturity period	1 year
Money market funds
Amortized Cost
Cash and cash equivalents	$ 109,155	103,992
Fair Value
Cash and cash equivalents	109,155	103,992
U.S. Treasury notes
Amortized Cost
Marketable securities, amortized cost	35,246	70,348
Fair Value
Marketable securities, fair value	35,251	70,342
Unrealized Gains and Losses
Marketable securities, unrealized gains	5
Marketable securities, unrealized losses		6
Equity securities
Amortized Cost
Marketable securities, amortized cost	1,220	1,220
Fair Value
Marketable securities, fair value	8,456	6,356
Unrealized Gains and Losses
Marketable securities, unrealized gains	$ 7,236	$ 5,136