Research and Development Agreements - Schedule of Research and Development Revenue from Related Party Relates to Revenue from Research and Development Agreements (Detail)

v3.19.2

Research and Development Agreements - Schedule of Research and Development Revenue from Related Party Relates to Revenue from Research and Development Agreements (Detail) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Revenue Recognition [Line Items]
Total research and development revenue	$ 5,211,000	$ 944,000	$ 11,624,000	$ 1,175,000
Takeda Development Agreement
Revenue Recognition [Line Items]
Total research and development revenue	5,000,000		11,100,000
Takeda Pharmaceuticals Inc
Revenue Recognition [Line Items]
Total research and development revenue	5,211,000	932,000	11,624,000	1,095,000
Takeda Pharmaceuticals Inc | Takeda Collaboration Agreement
Revenue Recognition [Line Items]
Total research and development revenue	0	81,000	0	92,000
Takeda Pharmaceuticals Inc | Takeda Individual Project Agreement
Revenue Recognition [Line Items]
Total research and development revenue	0	663,000	54,000	663,000
Takeda Pharmaceuticals Inc | Takeda Development Agreement
Revenue Recognition [Line Items]
Total research and development revenue	5,012,000	0	11,126,000	0
Takeda Pharmaceuticals Inc | Takeda Multi Target Agreement
Revenue Recognition [Line Items]
Total research and development revenue	$ 199,000	$ 188,000	$ 444,000	$ 340,000