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

v3.19.3

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		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Revenue Recognition [Line Items]
Total research and development revenue	$ 3,187,000	$ 2,031,000	$ 14,811,000	$ 3,206,000
Takeda Development Agreement
Revenue Recognition [Line Items]
Total research and development revenue	2,600,000	300,000	13,700,000	300,000
Takeda Pharmaceuticals Inc
Revenue Recognition [Line Items]
Total research and development revenue	2,903,000	1,914,000	14,527,000	3,009,000
Takeda Pharmaceuticals Inc | Takeda Collaboration Agreement
Revenue Recognition [Line Items]
Total research and development revenue	0	0	0	92,000
Takeda Pharmaceuticals Inc | Takeda Individual Project Agreement
Revenue Recognition [Line Items]
Total research and development revenue	0	1,246,000	54,000	1,909,000
Takeda Pharmaceuticals Inc | Takeda Development Agreement
Revenue Recognition [Line Items]
Total research and development revenue	2,581,000	253,000	13,707,000	253,000
Takeda Pharmaceuticals Inc | Takeda Multi Target Agreement
Revenue Recognition [Line Items]
Total research and development revenue	$ 322,000	$ 415,000	$ 766,000	$ 755,000