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

v3.19.1

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
	Mar. 31, 2019	Mar. 31, 2018
Revenue Recognition [Line Items]
Total Research and Development Revenue	$ 6,413,000	$ 231,000
Takeda Development Agreement
Revenue Recognition [Line Items]
Total Research and Development Revenue	6,100,000
Takeda Pharmaceuticals Inc
Revenue Recognition [Line Items]
Total Research and Development Revenue	6,413,000	163,000
Takeda Pharmaceuticals Inc | Takeda Collaboration Agreement
Revenue Recognition [Line Items]
Total Research and Development Revenue	0	11,000
Takeda Pharmaceuticals Inc | Takeda Individual Project Agreement
Revenue Recognition [Line Items]
Total Research and Development Revenue	54,000	0
Takeda Pharmaceuticals Inc | Takeda Development Agreement
Revenue Recognition [Line Items]
Total Research and Development Revenue	6,114,000	0
Takeda Pharmaceuticals Inc | Takeda Multi Target Agreement
Revenue Recognition [Line Items]
Total Research and Development Revenue	$ 245,000	$ 152,000