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Collaboration and License Agreements - Takeda Pharmaceuticals U.S.A., Inc - Additional Information (Detail) $ in Thousands		3 Months Ended
	Oct. 07, 2020 USD ($) Obligation Bundle	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Jan. 31, 2021 USD ($)
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenues		$ 21,303	$ 29,455
Takeda License Agreement \| License and Co-Funding Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Agreement date	Oct. 07, 2020
Ratio of Profit Sharing Structure for United States Commercialization	50/50 profit sharing
Number of distinct bundle \| Bundle	1
Number of distinct performance obligations \| Obligation	1
Initial transaction price	$ 300,000
Revenues		8,200	$ 0
Contract assets		$ 8,200
Takeda License Agreement \| License and Co-Funding Agreement \| Subsequent Event
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Cash received as due under collaboration agreement				$ 300,000
Takeda License Agreement \| Minimum \| License and Co-Funding Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Percentage of eligible to receive tiered royalties on net sales	20.00%
Takeda License Agreement \| Maximum \| License and Co-Funding Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Percentage of eligible to receive tiered royalties on net sales	25.00%
Development regulatory and sales milestones payments	$ 740,000