License and Collaboration Agreements (Details) $ in Thousands	1 Months Ended	12 Months Ended		21 Months Ended
	Apr. 30, 2018 USD ($)	Dec. 31, 2019 USD ($) item	Dec. 31, 2018 USD ($)	Dec. 31, 2019 USD ($)
License and Collaboration Agreement with Zai Lab
Revenue		$ 7,000	$ 5,000
Provision for income taxes		677	472
License and collaboration agreement with Zai Lab
License and Collaboration Agreement with Zai Lab
Upfront, non-refundable payment received	$ 5,000
Research support funding				$ 600
Certain other reimbursable clinical trial costs				600
Payment received, tax expense				1,900
Eligible amount receivable in research and development support payments and development, regulatory and sales milestone payments		$ 91,000		$ 91,000
Number of future milestones achieved | item		2
Revenue		$ 7,000	5,000
Provision for income taxes		$ 700	$ 500