Summary of Significant Accounting Policies - Segments (Details)	6 Months Ended	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2018	Dec. 31, 2017	Jun. 30, 2016
Segment Information
Number of operating segments		1
Bayer | Revenues percentage | Customer concentration
Segment Information
Percentages of revenue recognized				17.00%
CytomX | Revenues percentage | Customer concentration
Segment Information
Percentages of revenue recognized		8.00%	13.00%
Debiopharm | Revenues percentage | Customer concentration
Segment Information
Percentages of revenue recognized		2.00%	26.00%
Lilly | Revenues percentage | Customer concentration
Segment Information
Percentages of revenue recognized	4.00%	2.00%	1.00%	11.00%
Novartis | Revenues percentage | Customer concentration
Segment Information
Percentages of revenue recognized	24.00%	2.00%		1.00%
Roche | Revenues percentage | Customer concentration
Segment Information
Percentages of revenue recognized	60.00%	60.00%	24.00%	43.00%
Sanofi | Revenues percentage | Customer concentration
Segment Information
Percentages of revenue recognized			31.00%
Takeda | Revenues percentage | Customer concentration
Segment Information
Percentages of revenue recognized	8.00%	23.00%	4.00%	16.00%