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License Agreements - Additional Information (Detail) - USD ($)		1 Months Ended		3 Months Ended	6 Months Ended
	Aug. 31, 2016	Oct. 31, 2018	Sep. 30, 2017	Sep. 30, 2019	Dec. 31, 2018
Related Party Transaction [Line Items]
Percentage of Purchase Requirement				100.00%	100.00%
License and supply agreement notice period					90 days
Potential Regulatory and Sales-Based Milestone Payment | Maximum
Related Party Transaction [Line Items]
Milestone payment receivable amount	$ 444,000,000
Kyowa Kirin Co
Related Party Transaction [Line Items]
Upfront payment		$ 10,000,000
License agreement expiry period		10 years
Kyowa Kirin Co | Maximum
Related Party Transaction [Line Items]
Development and commercialization milestones payment		$ 87,500,000
Helsinn License Agreement
Related Party Transaction [Line Items]
Compensation Receivable For Grant Of Rights	$ 20,000,000
Presage License Agreement | Presage Biosciences, Inc.
Related Party Transaction [Line Items]
Compensation payable for grant of rights			$ 4,900,000
Payment for license			2,900,000
Presage License Agreement | Presage Biosciences, Inc. | Incremental Payment
Related Party Transaction [Line Items]
Compensation payable for grant of rights			2,000,000
Presage License Agreement | Presage Biosciences, Inc. | Potential Payments on Achievement of Development Regulatory and Commercial Milestones | Maximum
Related Party Transaction [Line Items]
Milestone payments payable amount			$ 179,000,000

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