Income Taxes - Operating losses and credit carryforwards (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Operating Loss Carryforwards [Line Items]
Foreign income tax holiday, term	15 years
Domestic Tax Authority
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	$ 55,029	$ 48,623
Tax credit carryforward, amount	1,818	3,359
State and Local Jurisdiction
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	79,907	65,412
Foreign Tax Authority
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	73,922	58,660
Tax credit carryforward, amount	$ 46,851	$ 46,851