Subsequent Events - License and Collaboration Agreement and Non-Exclusive Anticalin Platform Technology License Agreement with Seattle Genetics (Details) - USD ($) $ in Thousands		12 Months Ended
	Feb. 08, 2018	Dec. 31, 2017	Dec. 31, 2016
Subsequent Event [Line Items]
Milestone payments		$ 12,573	$ 1,655
Seattle Genetics | Subsequent Event
Subsequent Event [Line Items]
Contract termination due to material breach, additional notice period	90 days
Seattle Genetics | License and Collaboration Agreement | Subsequent Event
Subsequent Event [Line Items]
Period after effective date agreements may be terminated	12 months
Contract termination advance notice period	90 days
Agreement termination advance notice period if pivotal study has been initiated	180 days
Agreement termination notice period upon material breach by the Company	90 days
Seattle Genetics | License and Collaboration Agreement | Maximum | Subsequent Event
Subsequent Event [Line Items]
Milestone payments	$ 1,200,000
Seattle Genetics | Upfront Payment | Subsequent Event
Subsequent Event [Line Items]
Allocable arrangement consideration	$ 30,000