Collaboration and Other Agreements, Takeda (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended		6 Months Ended
	May 31, 2014	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015
Collaboration And Other Agreements [Line Items]
Deferred revenue included in current liabilities		$ 4,578		$ 4,578		$ 5,866
Deferred revenue included in long-term liabilities		10,740		$ 10,740		12,631
Takeda Pharmaceutical Company Limited [Member]
Collaboration And Other Agreements [Line Items]
Non-refundable upfront payment	$ 15,000
Takeda Pharmaceutical Company Limited [Member] | Research Collaboration And License Option Agreement [Member]
Collaboration And Other Agreements [Line Items]
Collaboration or other agreement date				September 2014
Amount allocated to agreement	5,000
Recognized revenue under agreement			$ 400		$ 700
Takeda Pharmaceutical Company Limited [Member] | Takeda MGD010 Agreement [Member]
Collaboration And Other Agreements [Line Items]
Collaboration or other agreement date				May 2014
License option fee		15,000		$ 15,000
Amount allocated to agreement	$ 10,000
Expected period of development				24 months
Recognized revenue under agreement		300	$ 1,200	$ 1,300	5,500
Milestone received					$ 3,000
Deferred revenue		800		800		2,100
Deferred revenue included in current liabilities		800		800		$ 2,100
Takeda Pharmaceutical Company Limited [Member] | Takeda MGD010 Agreement [Member] | Maximum [Member]
Collaboration And Other Agreements [Line Items]
Potential clinical and regulatory milestone payments		93,000		93,000
Potential sales milestone payments under agreement		$ 375,500		$ 375,500