License and Collaboration Agreements (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended		6 Months Ended		15 Months Ended
	Apr. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019
License and Collaboration Agreement with Zai Lab
Revenue			$ 5,000		$ 5,000
License and collaboration agreement with Zai Lab
License and Collaboration Agreement with Zai Lab
Upfront, non-refundable payment received, net of tax	$ 5,000					$ 5,000
Upfront, non-refundable research support funding, net of tax						600
Upfront, non-refundable certain other reimbursable clinical trial costs						300
Upfront, non-refundable payment received, tax expense						800
Eligible amount receivable in research and development support payments and development, regulatory and sales milestone payments		$ 98,000		$ 98,000		$ 98,000
Revenue		$ 0		$ 0	$ 5,000