Income Taxes - Operating losses and credit carryforwards (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Operating Loss Carryforwards [Line Items]
Foreign income tax holiday, term	15 years
Domestic Tax Authority
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	$ 48,623	$ 43,116
Tax credit carryforward, amount	3,359	901
State and Local Jurisdiction
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	65,412	38,307
Foreign Tax Authority
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	58,660	40,349
Tax credit carryforward, amount	$ 46,851	$ 42,755