Revenue - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2020	Dec. 31, 2019
Disaggregation Of Revenue [Line Items]
Revenue	$ 7,078
Accounts receivable	1,617	$ 813
Neurocrine Biosciences [Member]
Disaggregation Of Revenue [Line Items]
Accounts receivable	1,234
Deferred revenue	24,608
Neurocrine Biosciences [Member] \| Collaboration Revenue [Member]
Disaggregation Of Revenue [Line Items]
Revenue	7,078
Exclusive License to XEN901 and Exclusive License to DTCs [Member] \| Neurocrine Biosciences [Member] \| Collaboration Revenue [Member]
Disaggregation Of Revenue [Line Items]
Revenue	5,761
Development Services Under the Initial Development Program For DTCs [Member] \| Neurocrine Biosciences [Member] \| Collaboration Revenue [Member]
Disaggregation Of Revenue [Line Items]
Revenue	83
Research And Development Funding \| Neurocrine Biosciences [Member] \| Collaboration Revenue [Member]
Disaggregation Of Revenue [Line Items]
Revenue	1,234
License and Collaboration Agreement [Member] \| Neurocrine Biosciences [Member]
Disaggregation Of Revenue [Line Items]
Upfront payment received in cash	30,000
Upfront payment received in equity investment	20,000
Equity investment measured at fair value	16,667
Collaborate agreement premium related to equity investment	3,333
Revenue	$ 33,333
Percentage of option to co-fund development costs upon achievement of certain milestones	50.00%
License and Collaboration Agreement [Member] \| Exclusive License to XEN901 and Exclusive License to DTCs [Member] \| Neurocrine Biosciences [Member]
Disaggregation Of Revenue [Line Items]
Transaction price allocated to performance obligations	$ 28,807
License and Collaboration Agreement [Member] \| Development Services Under the Initial Development Program For DTCs [Member] \| Neurocrine Biosciences [Member]
Disaggregation Of Revenue [Line Items]
Transaction price allocated to performance obligations	$ 4,526

Amount, after allowance for credit loss, of right to consideration from customer for product sold and service rendered in normal course of business, classified as current.

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